Osedax, from the Latin os, oris (bone) and edāx, edācis (devourer), is a genus of undersea worms that consumes bone. A genus (which is more Latin, this time for a family group) is a group of species that are similar. More distantly, the genus Osedax belongs to the family Siboglinidae. Siboglinidae is a family (a level above in the biological categorization hierarchy from genus) composed of segmented worms, all of which have chitin bristles. Chitin is a natural substance that is found in all sorts of bugs, and it’s similar to the material that makes up your fingernails. Another prominent species in this family are the undersea tubal worms that live at the hydrothermal vents at the bottom of the ocean. It turns out there is a surprising amount of diversity of species of undersea bone eating worms. The worms range in size and in behavior. You can find members of the Osedax genus in all seven oceans, and in all sorts of depths (21 – 4000 m). Some of them are generalists, whereas others specialize in large bone deposits often found on the ocean floor. Whalefalls (you can read more about them here: http://chargedmagazine.org/2012/06/whale-fall-2/) are one such source of large bone deposits on the ocean floor.
Osedax worms were first discovered in 1994. Biologists were initially baffled at what exactly they were. The worms evaded classification until molecular DNA analysis showed that they were related to the tube worms that live in hydrothermal vents on the ocean floor. This breakthrough allowed biologists to finally place the Osedax genus into the Siboglinidae family. Later, fossils were discovered of Osedax worms inhabiting a large, dead reptile, dated to the early-Late Cretaceous period, about 100 million years ago. This led to several revelations about the history of Osedax worms. Firstly, there was now a historical precedent for being generalists, rather than whale specialists. Osedax worms were initially discovered and identified on whale falls, and there was some debate in the scientific community about whether or not they occupied other niches. Well, giant dead reptiles certainly weren’t whales, so this find cleared that up nicely. The fossil finding also illustrates something about the history of Osedax worms and the Siboglinidae family. This finding confirmed an earlier theory that the Siboglinidae family originated somewhere in the mid-Cretaceous period. It also means that the weird bone eating worms under the sea outlasted the dinosaurs, which is neat.
A labeled illustration of an Osedax worm.
Physically, Osedax worms are strange looking creatures. Red, string-looking bits float out from one side of the main worm body. On the other side, there are green, root-like structures sticking out back. These roots secrete acids to dissolve the bones where they lodge. Their middle is a white, segmented tube. It doesn’t get any more regular on the inside, either. Osedax worms don’t have a digestive system – they just host a wealth of bacteria inside of them to digest the bones they consume. Another strange thing about the inside of an Osedax worm is that the male worms live inside the females. As in, every picture of an Osedax worm you see will be of a female, as the males are teeny tiny and live inside of the females. Dwarf males, as this phenomenon is called, occurs when the males of a species are much smaller (and usually simpler anatomically) than the females. In species where dwarf males exist, the males typically reside somewhere inside or attached to the female members of the species. Osedax worms are at least as odd as you were expecting worms that ate bones to be, at very least.
References
Smith, Craig R, Glover, Adrian G, Treude, Tina, Higgs, Nicholas D, & Amon, Diva J. (2015). Whale-Fall Ecosystems: Recent Insights into Ecology, Paleoecology, and Evolution. Annual Review of Marine Science,7(1), 571-596.
Rouse, G. W. (2004). Osedax: Bone-Eating Marine Worms with Dwarf Males. Science (American Association for the Advancement of Science),305(5684), 668-671.
Danise, S, & Higgs, N. D. (2015). Bone-eating Osedax worms lived on Mesozoic marine reptile deadfalls. Biology Letters (2005),11(4), 20150072.
Some cats are oftentimes seen engaging in a rhythmic motion of pushing their paws back and forth on a soft surface, which is referred to as “kneading.” This behavior is not universal across all cats and can be distinctive among cats (“Why Do Cats Knead?, n.d.). The exact reason behind this behavior is a mystery, but there are a few explanations to rationalize this behavior (Castro, 2013).
Kittens knead their mother while nursing to stimulate milk flow. This behavior may be carried on into adulthood when cats are feeling happy, associating kneading with the comfort of its mother (Castro, 2013).
Cats may be marking their territories with their scent (“Why Do Cats Knead?, n.d.).
Female cats knead as a mating signal to males (“Why Do Cats Knead?, n.d.).
Kneading is a form of stretching (“Why Do Cats Knead?, n.d.).
Regardless of the reason why cats knead, we can all agree that they are super cute when they do so!
For as long as I can remember, I have been obsessed with how people move. Now, hear me out. Even simple movements are fascinating if you really think about it. Electrical signals from your brain and spinal cord communicating with hundreds of muscles, forcing them to work together in a perfectly balanced symphony of contractions. All to maneuver our unwieldy skeletons gracefully through space.
Do me a favor and stand up.
For most of us, this movement feels like one of the simplest things we can do.
Now, look at your legs.
There are over 50 muscles below your hips alone. Yet, all these muscles just contracted in expert harmony to use the precise amount of force needed to move your body against gravity, all while maintaining near perfect balance. Precisely how we can perform these seemingly simple yet crucial movements on a whim is an active and exciting area of research, leading us toward innovation in movement rehabilitation, robotics, and beyond. These are movements we don’t even notice, like activating our muscles to breathe, blink, maintain our balance, or even walk. If you did notice these movements, you likely wouldn’t be able to focus on much else, transforming a simple grasp into an impossible and difficult task.
Luckily, you don’t need your brain to do any of these things.
More than just a cord
Many people think of the spinal cord as just that, a cord. The cords and cables we typically interact with are charged with a very important but relatively simple task: bringing electricity from point a to point b. While the spinal cord is very important for bringing electrical signals from your brain to your muscles and organs, it does so much more.
Picture an orchestra with a smart but rather lazy conductor performing for an audience. The musicians are like the motor neurons in the spinal cord, connecting to and contracting the muscles when the neurons fire, allowing you to move. Complicated musical pieces require guidance by our lazy conductor, just like throwing a dart or grasping an object requires guidance by the brain [1]–[4]. The audience’s cheers allow the orchestra to adapt, just like you use sensations from your body to improve or guide movements [5], [6].
Yet, just like our experienced musicians don’t need the conductor to play simple or repetitive musical pieces, you don’t need your brain to perform “classic” movements. “The spinal cord is able to achieve so many behaviors by itself, completely isolated from the brain,” explains Dr. Cope, spinal cord neurobiology researcher and Georgia Institute of Technology professor. “You can completely isolate the spinal cord in a living animal from the brain and it can walk on a treadmill [7], [8]. It can change speeds as the treadmill changes speed. You put an obstacle in its way, it can learn to lift its leg over that obstacle,” all without our lazy conductor [9].
It was discovered in the early 1900’s that your motor neurons are fully capable of running the show [10]. “What that tells you is that there is this rich circuitry that in fact the whole motor system relies upon,” Dr. Cope explained. All in all, it looks like the spinal cord has the classics all worked out for you. Feel free to tell your conductor they can take the day off.
How to run around like a chicken with its head cut off
Unsurprisingly, experienced musicians are able to play complicated, intricate music without their conductor. Surprisingly to many, however, your spinal cord is able perform complicated, intricate behaviors without any input from the brain. How exactly are these behaviors possible? It’s all in the organization.
If you’ve ever gotten a physical, you have probably experienced the odd sensation of your leg flying through the air without your consent. In the right spot, a simple tap on your knee by the doctor sends your foot on a trip automatically. We commonly refer to these types of movements as “reflexes,” in which no approval by the brain is required. This reflex pathway is relatively simple in organization; only two neurons are required, making this one of the fastest reflexes we have. One neuron senses the stretch of your muscle caused by the tap and immediately tells the second neuron to flex that same muscle. This flexion rapidly moves your leg before you can stop to think about it. This can happen in less than a few milliseconds [11]! You use your stretch reflex more often than your visits to the doctor, however. The stretch reflex helps you keep your balance without a second thought and is believed to be crucial for general sensory feedback and movement control.
What if we make things a little more complicated? Instead of just two neurons, let’s add in two sets of neurons in the spinal cord: set A controlling muscle a, and set B controlling muscle b. Much like a seesaw, these sets of neurons rhythmically alternate in activity. A neurons fire until they run out of juice, then B neurons take over and the cycle continues. With this small set of neurons, a pattern of alternating activity emerges. Together, A and B neurons form a central pattern generator. For humans, however, a 2-muscle central pattern generator isn’t very useful. Adding in more sets of neurons allows your spinal cord to rhythmically control more muscles in a more complicated pattern. With anything from breathing and scratching an itch to walking and running, the spinal cord is in charge.
The patterns are there in your spinal cord, all you need to do is press start. “One of the things the brain does and can take full advantage of is to just send a ‘go’ signal to the spinal cord,” Dr. Cope explained. “[The brain] can say ‘Hey, all of the complicated things you do with timing and organizing … different muscles in different patterns, you do it. You’ve worked all that out. I don’t have to complicate my life with that.’” And while the brain can initiate and influence this pattern of alternating activity, it isn’t required. This pattern can just as easily be started by sensory input from your environment, or by sensory signals from throughout your body [9].
At the end of the day, it seems like the spinal cord has it all figured out for us. But do we have the spinal cord all figured out? Not even close.
The Mysterious Cord
In the past year, the news has been abuzz with instances of paralyzed patients regaining the ability to walk [12]. Paralysis is typically caused by spinal cord damage. Up until recently it seems, spinal cord injuries often left patients with limbs that were difficult or impossible to move willingly, oftentimes without hope for improvement. So how are these patients taking these miraculous steps?
A better question might be what happens to the spinal cord when it’s injured? We know some things about how it repairs itself, but we are far from the whole story. This means we are a far cry from fully repairing spinal cords ourselves. While these recent miraculous findings may make it seem like we have it all figured out, don’t let that fool you. “I think it’s exciting and I think it’s encouraging. I would say that we shouldn’t let our encouragement overshadow the fact that it’s nowhere close to what we want,” laments Dr. Cope. “It’s going to require some basic neuroscience information about what the mechanisms are that are limiting recovery.”
Researchers like Dr. Cope at Georgia Tech are working on a piece of this puzzle, studying to understand how the healthy and injured spinal cord contributes to and controls movement. Even with the great strides achieved recently by clinical studies [12], Dr. Cope explains that “We’re encouraged, but we have a long way to go.”
References
[1] D. P. Hanes and J. D. Schall, “Neural Control of Voluntary Movement Initiation,” Science (80-. )., vol. 274, no. 5286, pp. 427–430, 1996.
[2] D. M. Wolpert and Z. Ghahramani, “Computational principles of movement neuroscience,” vol. 3, no. november, 2000.
[3] D. A. Rosenbaum, K. M. Chapman, M. Weigelt, D. J. Weiss, and R. van der Wel, “Cognition, Action, and Object Manipulation,” Psychol. Bull., vol. 138, no. 5, pp. 924–946, 2013.
[4] E. Freud, S. N. Macdonald, J. Chen, D. J. Quinlan, M. A. Goodale, and J. C. Culham, “Getting a grip on reality: Grasping movements directed to real objects and images rely on dissociable neural representations,” Cortex, vol. 98, pp. 34–48, 2018.
[5] R. Shadmehr, M. A. Smith, and J. W. Krakauer, “Error Correction, Sensory Prediction, and Adaptation in Motor Control,” Annu. Rev. Neurosci., vol. 33, pp. 89–108, 2010.
[6] D. M. Wolpert, Z. Ghahramani, and M. I. Jordan, “An internal model for sensorimotor integration,” Science (80-. )., vol. 269, no. 5232, pp. 1880–1882, 1995.
[7] T. G. Brown, “The Intrinsic Factors in the Act o f Progression in the Mammal,” Proc. R. Soc. London. Ser. B, Contain. Pap. a Biol. character, vol. 84, no. 572, pp. 308–319, 1911.
[8] S. Grillner and P. Zangger, “On the Central Generation of Locomotion in the Low Spinal Cat,” Exp. Brain Res., vol. 261, no. 34, pp. 241–261, 1979.
[9] E. P. Zehr, “Neural Control of Rhythmic Human Movement : The Common Core Hypothesis,” Exerc. Sport. Sci. Rev., vol. 33, no. 1, pp. 54–60, 2005.
[10] C. S. Sherrington, “Flexion‐reflex of the limb, crossed extension‐reflex, and reflex stepping and standing,” J. Physiol., vol. 40, no. 1–2, pp. 28–121, 1910.
[11] E. G. T. Liddell and C. S. Sherrington, “Reflexes in response to stretch (myotatic reflexes),” Proc. R. Soc. London. Ser. B, Contain. Pap. a Biol. Character, vol. 96, no. 675, pp. 212–242, 1924.
[12] P. J. Grahn et al., “Enabling Task-Specific Volitional Motor Functions via Spinal Cord Neuromodulation in a Human With Paraplegia,” Mayo Clin. Proc., vol. 92, no. 4, pp. 544–554, 2017.
Cats are one of the most popular choices as human friends, and I absolutely adore them! I hope to have a feline friend in the future and hopefully, you will too if you don’t have one already. Among all the cute actions that these creatures engage in daily, there are some anomalies that make their human friends ponder. These fun facts may answer a question or two you’ve had and enlighten you with the uniqueness and awesomeness of cats.
The cats we have in our homes are really similar to wild cats!
Compared to dogs, cats have been domesticated for only half as long and still engage in behaviors similar to wild, big cats such as lions and tigers. Their genes have not changed much from that of wildcats, except for one distinguishing factor: the coat patterns seen on the tabby cat (“Cats Domesticated Themselves, Ancient DNA Shows,” 2018).
Cats cannot taste sweetness.
Like humans, cats are able to taste saltiness, bitterness, sourness, and umami! The genes Tas1r2 and Tas1r3 allow sweet tasting in mammals by encoding sweet sensing receptors. Cats have both of these genes, but their Tas1r2 gene, however, is a pseudogene, or nonfunctional copies of a functional gene (Li, Li, Wang, Bayley, Cao, Reed, Bachmanov, Huang, Legrand-Defretin, Beauchamp, and Brand, 2006).
Why do cats kill unbelievable amounts of mice and birds?
As natural-hunters, cats still carry unstoppable instincts that they’ve had thousands of years ago. Female cats are also found to engage in hunting more often to teach their young how to acquire food and feed (Palermo, 2013).
Cats will bite in response to being overstimulated, not because they hate you!
Overstimulation typically occurs in attention-seeking, friendly cats. When these felines are continuously being pet, it appears that there can be a buildup of stress for these animals leading to aggressive behaviors. Cats may give some warning signs before their impending aggression such as a continuous, whipping tail, flattened ears, and a tense body (“Overstimulation in Cats,” n.d.).
Cats meow only to communicate with humans!
Meows are usually found in kittens that need to communicate with their mother. However, communication between older cats consists of growling and hissing. Meowing is exclusively used by felines to tell their humans if they may be hungry, stressed, or needing attention (“Cats and Excessive Meowing,” n.d.).
Cats sleep a lot, but why?
Cats sleep up to 16 hours a day – that’s 67% of the day! This is because they need energy for hunting-like behaviors such as pouncing and chasing (Cespedes, n.d.).
Cats are crepuscular, so their schedules are completely different from humans.
They are most active at dawn and dusk, and often nap during the day while basking in the sun (Cespedes, n.d.). Though this is their natural schedule, cats may adjust their sleeping to fit their owner’s schedule.
Why do cats bury their excretions?
Burying waste is an instinct that cats have in order to mark their territory and avoid attention from predators (Melina, 2011). Their excretions have unique pheromones, making it possible for other cats to differentiate it from their own waste.
Cespedes, Y. (n.d.). Retrieved from https://www.petmd.com/cat/behavior/evr_ct_why_do_cats_sleep_so_much
Li, X., Li, W., Wang, H., Bayley, D. L., Cao, J., Reed, D. R., Bachmanov, A. A., Huang, L., Legrand-Defretin, V., Beauchamp, G. K., … Brand, J. G. (2006). Cats lack a sweet taste receptor. The Journal of nutrition, 136(7 Suppl), 1932S-1934S.
Melina, R. Why Do Cats Bury Their Poop? (2011, March 23). Retrieved from https://www.livescience.com/33147-why-do-cats-bury-their-poop.html
Overstimulation in Cats. (n.d.). Retrieved from http://www.treehouseanimals.org/site/PageServer?pagename=caring_ccg_overstimulation
Palermo, E. Why Do Cats Bring Home Dead Animals? (2013, March 29). Retrieved from https://www.livescience.com/34471-cats-dead-animals.html
Surprising Things You Never Knew About Your Cat. (2015, December 03). Retrieved from https://news.nationalgeographic.com/2015/12/151203-cats-animals-science-communication-pets/
Have you ever wondered what a raindrop would taste like if it was transformed into cake form? Look no further! Raindrop cake, albeit very different from your typical, traditional cake, will let you have a truly magical experience. My first attempt!
My second attempt!
I’ve always loved scrolling through food reviews and videos. One trend that emerged in recent years caught my eye. It was a clear, beautiful jelly bubble resembling a raindrop. It seemed so unique that I set out on a journey to try creating it myself, and it was definitely not an easy task. Being able to set the cake while trying to keep it light, soft, and bouncy and to where you’re able to feel like you’re eating a drop of water took many trials and errors. Keep reading to discover more about the secret ingredient and how you can make your own raindrop cake!
Raindrop cake, also known as Mizu Shingen Mochi, was first created by the Kinseiken Seika Company in Japan, using two main ingredients: fresh, mineral water from the Japanese Alps and agar. This light, refreshing delicacy resembles a jiggly, blob of jello, but will melt in your mouth and fill it with a hint of sweetness and nuttiness when paired with brown syrup and roasted soybean flour. But beware! If not eaten immediately, this dessert will dissolve and vanish within 30 minutes as recipe calls for the minimal amount of agar.
The key ingredient that solidifies water into a raindrop cake is a polysaccharide known as agar-agar. Agar is made from seaweed or red algae, Gelidium amansii. It was first introduced in Japan over 350 years ago, in 1658, and is still commonly used to this day due to the hydrocolloid properties and agarose composition that allow it to form gel-like substances using hydrogen bonding in the presence of water. Agar is also unique in that its thickening properties are reversible; disintegration occurs when temperatures are varied.
The structure of agar.
Due to agar’s gelling ability and the ease at which substances can be gelled, melted, and reformed, agar has numerous uses. One of the most common applications of agar can be found in the food industry. Agar is used in canning foods and is also tasteless, making it a perfect addition to foods and desserts that need thickening such as ice cream, icings, puddings, cookies, jelly, and pie fillings. It can also be found as an agar jelly or as a crystal boba topping in many bubble tea drinks. It has also been used as a laxative and in diets due to its ability to stimulate fullness using low calories.
Agar jelly used as a topping for bubble tea.
This was the first time I’ve ever had agar jelly, and I haven’t looked back since! Yum!
Application in biology labs as a medium to breed insects like silkworms and fruit flies or to culture bacteria and yeasts is also common.
Agar is a valuable ingredient for many reasons such as being extremely low in calories and containing fiber. Agar also does not require sugar to solidify, which is highly beneficial in food preparation for diabetics. It is also known as a vegan and vegetarian gelatin substitute, and best of all, it is an environmentally friendly product.
Here’s how you can make your own raindrop cake that has swept the internet in recent years!
Ingredients
1 cup of mineral water
1/4 tsp agar-agar
3 tsp of granulated sugar (optional)
Optional toppings
1 tbsp roasted soybean flour
brown sugar syrup (1 cup of brown sugar + 1/2 cup of water)
flowers, petals, fruits
Dissolve agar and water in a small pot.
Allow mixture to come to a boil over medium-high heat. Continue boiling over a medium heat for 1-2 minutes.
Pour mixture into any round-bottom mold. (Optional: Add light fruit/flower toppings to the mixture.)
Let mixture cool and place in the fridge overnight or until it sets.
To make syrup, dissolve the brown sugar in water over medium-high heat until mixture boils. Maintain a rolling boil for 1 minute.
Remove mixture and let cool. Serve with raindrop cake along with optional soybean flour. *Consume your raindrop cake upon taking it out the fridge. May melt if left out for over 20-30 minutes.
References
Giant Raindrop Cake Recipe by Tasty. (n.d.). Retrieved from https://tasty.co/recipe/giant-raindrop-cake
K. (2018, September 15). Raindrop Cake. Retrieved from https://kirbiecravings.com/raindrop-cake/ Maitland, H. (2017, August 02). Everything You Need To Know About Raindrop Cakes. Retrieved from https://www.vogue.co.uk/article/everything-you-need-to-know-about-raindrop-cake
National Center for Biotechnology Information. PubChem Compound Database; CID=71571511, https://pubchem.ncbi.nlm.nih.gov/compound/71571511 (accessed Sept. 28, 2018).
Phillips, G.O. Williams, P.A.. (2009). Handbook of Hydrocolloids (2nd Edition).Woodhead Publishing. Retrieved from
https://app.knovel.com/hotlink/toc/id:kpHHE00002/handbook-hydrocolloids/handbook-hydrocolloids
Exams……projects……homework assignments, it never ends! In turn, the anxiety begins to manifest. According to the National Institute of Mental Health, an estimated 19.1% of U.S. adults had any anxiety disorder in the past year.
Sadly, for many yellow jackets, anxiety has become a normality. This emotional response is mostly associated with the fear of not doing well academically at Georgia Tech. Most of us don’t know why we can’t stop worrying. Many of us look past our anxiety and think this is normal, especially when you hear other students complaining about the same things you are. However, when it gets to the point of where the anxiety interferes with your life, it’s time to take action and understand your neurological chemistry.
Anxiety is a feeling that lingers ling after a stress (external stimulus that signals danger often by causing pain) has lifted and the threat has passed. The factors that trigger anxiety grow out of a response that is hardwired in our brains. For example, thinking you won’t be successful if you don’t do well and pass a class. When in reality, one class doesn’t determine our future. But why do we think this way? Are we born this way or do our experiences cultivate our thinking?
Kenneth Kendler, a psychiatric geneticist, decided to approach this question by studying groups of identical twins who share virtually all their genes, and fraternal twins, who, like any other siblings, share only some of them. What Kendler’s group found was that both identical twins were somewhat more likely than both fraternal twins to suffer from generalized anxiety disorder, phobias or panic attacks. The correlation isn’t 100%, however. “Most of the heritability is in the range of 30% to 40%,” Kendler says. That’s a fairly moderate genetic impact, so your genes set your general vulnerability. But your upbringing and your experiences still have a major role to play.
Being that we have no control over our genetic makeup, how can we turn their negative anxiety into positive anxiety? Using it as a tool to focus the mind. Think about it, when you’re worried, anxious, or fearful, whatever you’re associating these feelings with consume your thoughts and you can only focus on that discomfort. To change this, one would need to explore their amygdala and hippocampus. The amygdala tells the body what to do while the hippocampus is a cluster of nerves that help the brain learn and form new memories. These new memories will activate the prefrontal cortex which sends out an “everything is ok,” message, and lets the amygdala know that there is no reason to worry or cause anxiety. So instead of thinking negatively, think something positive no matter the situation or circumstance. Just like any habit, it’s easier to stop than it is to start, so it will require intentional effort to clear your mind of negativity. Understanding this neural circuitry can be the key to reduce the anxiety of students at Georgia Tech and increasing the jubilation of students.
Gorman, C. (2002). The science of anxiety. Time Magazine, 47-54.
At some point, modern humans started believing that we are somehow special, that we are the center of creation and of the universe and that God loves us most. My point isn’t to argue against such divine egocentricity; we are indeed very special. Hell, no other species has made guns and missiles and stuff. And we are special even from a biological perspective. The reason we’ve done so well as a species is because we have adaptations that have allowed us to do so. So what are they?
We have many. Vertical skeletal structure, opposable thumbs, massive frontal cortexes, and unlimited salad and breadsticks are all commonly cited as being necessary for our species to thrive and dominate. These are all important morphologies. I believe, however, that there is one very overlooked adaptation in our evolution, one thing that, if it weren’t just right, would negate all of the benefits from these other lesser adaptations. So if it’s not our massive brain or our dexterous hands, what is it? Turns out it’s guns and missiles.
Guns and missiles have allowed humanity to reach far beyond our former niche. We now own the planet with such unchecked power that one person can say “I want to blow up that bit of the surface right there”, and his buddy thousands of miles away can instantly reply, “done!”. This adaptation has caused an evolutionary cascade of intermittent……………..ok, I can’t keep this up. I’m full of it. Our most important adaptation is actually our size.
I guarantee that human size was not the first adaptation that would have popped into your brain, but it is arguably the most important. Am I suggesting that all animals our size are evolutionarily successful? Of course not. Am I saying that tiny or huge people are somehow inferior biologically? Nope. However, if we were, on average, significantly larger or smaller, like ten times as large or small, the course of earth’s history probably would have played out very differently.
Much like the famous fairytale porridge, we benefit from being “just right”. Being the right size means there’s space for a brain that prioritizes and categorizes and tells the body to act judiciously. We stand vertically because we’re small enough not to battle gravity as ferociously as we would if we were the size of elephants. We can offer unlimited salad and breadsticks because we’re large enough to farm yet small enough to be incapable of eating the planet’s supply of breadsticks in one sitting. In this article of Badass Biology, I hope to convince you that our dominance stems from our ideal size. Had we been much larger or smaller, the evolution of our intelligence would have played out much differently, meaning no guns and missiles.
Bigger is better, unless you’re Godzilla
What does size have to do with anything? As animals grow larger in size, they tend to become more metabolically efficient. A cornerstone of evolutionary theory lies in Kleiber’s “3/4ths power rule”, stating that for every added unit of mass, metabolic rate only increases as a rate of mass^(3/4) [1]. While the value of the exponent and its real-world meaning is debated, one thing is clear: grow larger, and you’ll use less energy for your size, a comment you also hear regularly from your disappointed girlfriend.
Humans are damn gigantic; 99% of all animal species on earth are smaller than we are [2]. Does the power rule work to our advantage? Yep. Because math. The average human male (7700g) weighs roughly 457 times that of a typical field mouse (15g). Raise both to the ¾ power, divide one by the other, and you’ll find that the human has only about 100 times the metabolic demand of a field mouse despite the 457 fold increase in mass. I’d say that gives us a pretty big advantage in terms of having to spend less time and energy feeding, replacing tissues, respiring, etc. More time for guns!
ENDOTHERMS!! WOOOOO!!!
This sounds great, but if bigger is better, why isn’t every animal huge? Again, because math. Think back to high school geometry. Among the suppressed memories of sitting behind that brunette you thought was cute but wouldn’t pay attention to you unless you were captain of a team sport but that you later reconciled with because she ended up being a relatively heartless and shallow person despite her extreme self-professed piety, or that guy across the room you thought was an asshole to other people because he had a giant triangular face and douchey long blonde hair and a name not unlike “Brittney” until he confirmed his assholiness by being an asshole directly to you about something that absolutely did not matter at all, surely you must remember the formulas for surface area and volume. Basically, a shape that grows larger and keeps its form expands its volume in three dimensions (side x side x side), whereas surface area expands only into two (side x side). Big objects, like animals or guns or missiles, have relatively low surface area compared to their volume because volume mathematically outpaces surface area as objects grow bigger.
This is a really big deal. Think about every process that keeps you alive. Breathing, eating, sensing your environment, playing Civilization 5. All of these processes rely on tissues with some kind of exposure to the outside environment. Oxygen is absorbed as air rushes across alveoli in the lungs. Nutrients are absorbed through countless tiny folds of the small intestine. Tastants and odorants absorb through fluid media in the mouth or nose to trigger sensory receptors. Civilization 5 enters your brain through tiny refractive holes in the middle of your face. These are all parts of your surface area.
The point is this: if we were a lot bigger, like Godzilla-sized, we’d have a lot of trouble performing these same basic functions given our current body shape. This would suck for the most part. We’re already pretty specialized as is; a lot of animals don’t have folds in the lungs or intestines like we do because they’re small enough (thus having enough surface area for their volume) not to need them. But not absorbing things would be only one of our many worries if we were larger.
The earth’s gravity is not all that strong in a cosmic sense, but its impact on surface-dwelling body forms is huge. Let me put it simply: stuff caint grow too big because aint no way they caint get strong enough to stand up. Fighting gravity is hard unless you’re a gun or missile, especially when you’re giantic. Our skeletons would have to be quite different in order to support our huge stature. Bones would need to be thicker yet more pliable.To be Godzilla-sized would be risky, not only because of the inevitable bone weakness and joint decay, but because of imbalance and falling. Even at twice our current size, tripping over a gun or missile would cause a tumble with 16 to 32 times more kinetic energy than it would now.
This all sounds like a recipe for disaster.
Suppose that our bodies do adjust. We grow to Godzilla size, have super-efficient perforated lungs, guts that absorb enough to get by, and bones capable of supporting a small skyscraper that can walk and build guns and missiles. Imagine the caloric demand a body like that would require. How many hamburgers would we need to eat in a day?
Godzilla is, at lowest estimates over his career, 164 feet tall, or about 50m. A quick foray into ideal body weight calculations yields that a 25-year old male this height should weigh around 8106.8 pounds, or 3676ish kg. Plug that into the ¾ power formula, and the daily metabolic demand of our gargantuan is around 84,000 calories per day. The power rule certainly works into this huge person’s favor, because I certainly was disappointed by how low that caloric count was. So what does 84,000 calories look like? Imagine 81 quarter pound hamburgers with white wheat buns, ketchup, and a tomato slice. And that’s only just breakfast; imagine eating that three times per day. BIG PEOPLE PROBLEMS. I’m sure I’ve made my point. The earth would strain to support life of that magnitude. Here’s the kicker: I didn’t even account for added bone mass and musculature necessary to become that tall. Let’s add another 100,000 hamburgers per meal to the calculation just to be safe.
The worst part of being tall would be this: it would be really hard to fit as many people onto airplanes. The airline industry wouldn’t see as much profit from airfares, thus flying would be a privilege only for the super-rich, limiting my ability to go to places like Switzerland. And I really want to go to Switzerland.
I am convinced that Mürren is one of the most beautiful places ever. I encourage my rich philanthropist readers to take note. Did I mention how starving I am?
Why Ant-man is the worst superhero ever.
What if we were much smaller? Well, there’s good and bad news. The good news is that we could adopt simpler body forms, but that’s about it. The bad news? Pfft.
First. we would probably be much dumber than we are. Zoom in closely on the brain of every animal and you’ll find neurons, cells that communicate to one another using electrical or chemical signals. Hundreds to thousands of these neurons form dense and complicated circuits with one another in the vertebrate brain. Such circuits form pathways that tend to perform specific functions in the body. For instance, there are specific regions of the brain designated for movement, for regulating sleep, for hunger, for balance, for typing “guns and missiles”, and for interpreting the sights, sounds, and smells from the world. Our bodies may be able to shrink in size and still function to some degree, but our neurons cannot only be miniaturized and still function with such complex synchrony and elegance. As we grow significantly smaller, we run out of room for neurons very rapidly.
“But Kevin, I’ve always heard that a big head doesn’t mean make you smarter”. Don’t you sass me. But you are right, anonymous naysayer. There is admittedly weak evidence that intelligence correlates with head volume, yes, but that’s among humans of relatively the same size [3]. For example, my fiancée is tiny and adorable, though she’s likely smarter than I am (Fiancée et al, 2014). However, when we’re talking about a difference in scale between us and a mouse, size matters. We have nearly half the number of neurons as the U.S. military has guns and missiles, something around 86 billion neurons [5]. Mice have around 10 million. Ants have around 200,000. To put this into perspective, if each neuron were a person, our brains would outnumber earth’s human population 12 times over. A mouse’s would be constrained to the size of North Carolina. An ant’s would be Laredo, Texas. It’s hard to grow intellectually when you’re Laredo, Texas.
I apologize to anyone from or living in the city limits of Laredo. I did not mean to say your city is dumb. However, it certainly looks that way. I’ve visited your website. It looks terrible.
Come to Laredo and visit our…moon.
Being the size of an insect would present a number of other challenges. The interactions we have with things in our environment (like the water we drink and the food we eat) conform to the laws of physics. As we shrink in scale, these interactions change. To an ant, water seems as viscous as maple syrup. Gravity takes a backseat to air turbulence. As Steven Jay Gould writes, “An ant-sized man might don some clothing, but surface adhesion would preclude its removal. The lower limit of drop size would make showering impossible; each drop would hit with the force of a large boulder. If our homunculus managed to get wet and tried to dry off with a towel, he would be stuck to it for life. He could pour no liquid, light no fire…” [2].
Could an ant-sized version of early man have developed civilization even if intelligence were not a factor? Probably not, at least not at the same rate or with the same level of success. I imagine cultivating agricultural crops, one of the supposed precursors for civilization, would have been near impossible, not to mention cross-breeding them for good yield. Our meat-based diet would be replaced with who knows what, but I suppose it would include plant material and any nearby organism that decides to die. For that matter, hunting would be folly; spears and bows would be completely ineffective because we probably couldn’t put enough force behind the blow. Guns and missiles wouldn’t exist. Our predators would vastly rise in number, distancing us from the top of the food web. We’d be stomped into submission by the elements, by other creatures, and by our own ineffectiveness. Switzerland would be near impossible to get to. So long, Mürren.
What about food? Shouldn’t food be more abundant since, you know, one kernel of corn could feed an entire village of people? That’s true, but there’s a much bigger caveat to this than you’d think. The world’s food is spatially patchy. I don’t just mean that bananas only grow in the tropics or that rice grows best in silty soil. I mean that, when you’re the size of an ant, getting a bug from the ground nearby is a marathon. Food sources are really f**king far apart, but plentiful once they’re found. Many animals that live upon such food sources adopt life strategies to cope with smorgasbord-style resources. Some insects that exploit huge but infrequent foods, including flies like the gall midge, have adaptations that allow them to exploit them quickly. Gall midges typically reproduce sexually, though it takes a long time for larvae to develop this way. When midges find a mushroom, a gold mine on their scale, females reproduce without a male through a process called parthenogenesis. These offspring are formed more quickly than doing things via the sexual route, though it comes at a cost to the mother. Instead of developing externally, the larvae grow inside the mother, eventually liquefying her insides and bursting from her lifeless husk [4]. However, immature as they may be, they are ready to start chomping away on some sweet sweet mushroom bits and rotting parts of their mommah. D’awww. Overall, the flies have more successful babies this way, thus the need for bursting out of their moms and such.
Will humans do that? I dunno. That sounds desperate. But food would likely be lacking for most humans on earth. Maybe we’d be as successful as ants and develop complex chemical signals to communicate the locations of food, bypassing any other weird adaptations like the ones midges have . Maybe we wouldn’t, and we’d fill just another tiny niche in the complex world which we inhabit.
So, I hope you now understand how important our size is for our survival. We are big and scary creatures, and that’s allowed us to hunt and kill and eat meats and make pizzas and build guns and missiles. But we’re not so large that joint damage, eating entire herds of cattle per day, and toppling over and breaking bones would be a daily norm. We’re also not so small either that we can’t take showers or cultivate food. So, here we stand, results of the goal-less, powerful, yet delicate hands of natural selection. Just right.
Nobody comments on my stuff. You should comment on my stuff. Get your friends to comment on my stuff. I will then comment. We can all comment. It will be a great world full of comments.
WE HAVE GUN AND MISSILE CONFERENCES!!! HUMANITY, BITCHES!!!
As a US citizen who travels internationally to conduct research, I’m well aware of the perception that gringos = $$. Sometimes that perception is true and you have money on your person or have access to it. But sometimes you simply represent wealth in some sociocultural way. Regardless of the reason, the fact is that I get robbed sometimes. Getting robbed is no fun, but it does make for some good stories.
Robbers are opportunistic, and travelers are, by definition, out of their element, so opportunities arise to rob travelers. Robberies are also about communication, i.e., “Give me your money now.” Pretty simple, huh? Well, sometimes the solution (i.e., not getting robbed) can be just as simple. If the robber doesn’t speak English and the robbee pretends not to understand the phrase “Give me your money now” then the would-be robbery is at a communications standstill. This dumb gringo trick works great, and I’ll use it as long as no weapons or physical assaults are involved. Before I developed this trick, however, I did wind up engaging a robber in a conversation in his native language.
I was out in the Neotropical boondocks very late one night alone in the rain, catching toads (it’s what I do). A guy on a horse came up behind me and startled me. Yeah, I get really focused on toads, so scenarios like this can happen; and, I don’t hear well. I assumed that I had accidentally trespassed onto his land, so I initiated the conversation of apologizing if I had done so, and promising to leave immediately if I was out of place. Turns out he did not care at all where I was, but he did want to rob me. Immediately, I was kicking myself for making the evidently poor decision a few hours earlier, to put my entire research-travel grant funds in my pocket, rather than leave them in the truck on the highway. Eventually, after a long conversation, I convinced him that my boss (who did not exist) had all of the funds back in the fancy hotel in the capital city because no one with lots of money would ever trust it to some schmuck pathetic enough to be hired to catch toads on a rainy night with all these mosquitoes around. I showed him my bag full of toads as evidence of the veracity of my story. He agreed that this made sense, and then demanded my flashlight. So, I asked him please not to take my flashlight, because then I couldn’t even do my shitty job and I’d get fired. He got off the horse, gave me a hug, and said something to the effect of, “I’m sorry for you my friend, as your lot in life is even worse than my own.” Of course he had a machete, because he was an actual cowboy, but he never raised it at me. If he’d raised that machete, he would have had a few hundred dollars instantly.
So, not all robbers are necessarily bad people. But I’ll tell you who are bad people: corrupt government officials. As robbers, they have a huge advantage and they know it. They have, ironically, the authority of law on their side, and the mere threat of being arrested during my travels is scarier than any gun I’ve had shot in my direction. These guys always have guns. They also have the mandate to set up roadblocks and stop all cars in the name of programs like the War on Drugs. For the corrupt ones, their day job is to make sure that the only people carrying drugs and weapons on that road are the people from the pre-approved local cartel. So they are not kidding when they search or grill you hard about carrying unauthorized drugs or weapons; just don’t conflate their diligence with caring about preventing drug trafficking. Once they clear you at the roadblock, they sometimes settle into robber mode. This authoritarian backdrop makes for some effective robbing. The game becomes a push-and-shove of “how little can I give them” vs. ”how much do I think this guy has on him.” To their credit, they are smart enough to realize that they have to be practical and discrete about all of this because if they just carjack you and take everything, then well it would be awkward to have you sitting there on the curb, and they have the keys to your truck, but they can’t take off with your truck until the end of their shift. These guys are not dumb thugs. They are fully aware of their advantage and thus are really impatient with any attempts you may make to stall the obvious outcome. In other words, I tried the dumb gringo trick at a roadblock exactly once. It escalated very badly, and they got all my money. Lesson learned.
The wandering toad-seeker runs into other brands of robbers as well. Gas station attendants can make a great cover for a top-class grifter. These folks have all day every day to figure out new, and often ingenious, tricks to rip off the customer. Again, they have an advantage on their side. You stopped and engaged them in this transaction, you need the gas that only they can access, and at some point you are going to give them the amount of money that they say you owe them. Add in the ever-bumpy cultural and language barrier plus, in my case, raging dyscalculia, and they definitely have the upper hand. If you do not pay them what they say you owe them, then you are stealing which is illegal (see “getting arrested” above). What are you going to do…drive off without paying? I dare you. The solution is to learn the more obvious scams and block them before they can play out.
Hookers are a complex reality. I want nothing to do with hookers, but, as a male gringo, they come to me. Remember gringo = $$ and, I usually wind up spending a lot of time politely declining the well-crafted and earnest sales pitches of hookers who assume I am rich. One night, however, the terms hookers and robbers became synonymous. After a moderate round of drinking in a large tropical city, my gringo colleague and I were walking back to our shabby hotel. He picked the route back, I argued against it because it seemed sketchy, but he won the argument. So I’m crossing the dark lonely back alley that people like me know to avoid and suddenly I am physically surrounded by three hookers who are busily putting their hands in my delicate areas and busily cramming my own hands into their delicate areas. There are eight hands involved here. My two hands are “occupied” against my will and the other six hands are occupied with violating my privacy and rifling through my pockets. Take-home advice: don’t wear baggy shorts in sketchy neighborhoods at night. It was over in seconds and they were gone. I’m not dumb, so I didn’t have my passport or watch or anything like that on me. They got my six leftover dollars that I had not spent on beer. Ok, so I got mugged or whatever, and they got six dollars. No one got physically hurt, and it was far less terrifying than the threat of getting arrested by corrupt cops. What was really terrifying was my first response to the assault: I launched into my rote spiel politely declining their sales pitch. That is how off-guard I was to the actual situation; it didn’t even occur to me to fight back, or run, or scream or anything remotely more rational than essentially saying “no, thank you.”
Afterwards, and to this day, the truth slaps me hard. I wasn’t being solicited, I was getting robbed. And whether the robber is a street thug, an official, a grifter, or a lady of the night, the victim is always the same: the hapless gringo perdido.
Vision is awesomely complicated. A lot of animals, like the hawk, use vision to detect important environmental cues from vast distances. They use complex eyes and even more complex brains to locate prey, or figure out where the ground starts, or I dunno, check out lady hawks. Hearing is like vision’s less-popular but talented younger brother, the often-forgotten Luigi to evolution’s Mario. Hearing is amazing, yes, but our hearing kinda sucks. We’re not good at it, and so we discount its importance. Instead, we glorify vision as the pinnacle of evolutionary achievement, the ultimate sensory weapon against a hostile world. Yes, vision is awesome, and it is reliable, and it is useful for things like looking at steak. I f**king love steak. But other animals use hearing to see their steaks oh man that sounded really stupid so now it’s a run-on sentence now I don’t know how to end it oh no I’m embarrassed lol. The bat is one of the few animals that can accomplish this awkwardly-written steak hearing, and it does so using methods that absolutely amaze me.
It must not come to a shock to you that bats use echoes from their own calls to create a mental picture of the world around them. Bats hear with the precision of a rocket-tipped arrow, which sounds totally stupid because that implies the rocket should blow the arrow backwards and that’s not where the pointy end is, but this is not important. I will explain to you how they use variable auditory frequencies, interaural timing, Doppler shift, and badass brain parts to make a map of their world. In short, they use magic. Bottom line, bats are badass.
PARTS OF THE ECOCHOLOCATION PROCESS THAT ARE BALLS-OUT INSANE BECAUSE THEY GIVE BATS THE HEARING PRECISION OF A ROCKET-TIPPED ARROW.
1-The call
Did you also know that bats are really damn good at determining object size, velocity, shape, and even if it’s fluttering? I bet you didn’t, Mr. Fact Learner. You need to learn up all of your facts except that fact because you know for a fact that this fact is a fact, and that’s a fact.
Small bats usually emit two types of calls. First up are frequency-modulated (FM) sweeps, and bats use these to locate objects in the space around them. These calls are usually quick, and the pitch rapidly drops. This allows bats to emit a range of frequencies to the nearby area. The amount of time an FM sweep takes to return to the bat allows the bat to determine distance. Bats also use the time disparity between frequencies in the left and right ears to tell where objects are on the azimuth, or how left/right they are relative to the head. The pointy shape of their ear also allows bats to use FM pulses to gauge the elevation of objects.
We got three properties down in one paragraph: azimuth, elevation, and distance. Isn’t that enough? Hells nah. They use some of them AT THE SAME TIME. For instance, bats can tell the size of an object by determining how loud the echo is. They can then use all of this information to tell the difference between something like a bird that’s far away and a moth that’s up close. FM calls are sweet.
The second type of call allows bats to tell how fast an object is moving. Constant-frequency (CF) pulses are typically longer, though the pitch does not drop. This allows, and yes I’m serious, bats to determine slight deviations in pitch due to the Doppler effect; a CF echo from an approaching object is slightly higher in pitch. This raises a good question: How can a bat do this if it’s flying toward an object? Wouldn’t the act of approaching an object make the CF pitch higher simply because the bat is moving towards it?
FM and CF calls from two species of bats. Notice how quickly the pitch decays in the FM calls, whereas the CF calls sustain one pitch for some time. Some species even have FM and CF components within one call. Pretty sweet.
This next experiment sounds kind of insane, but I promise it really happened.
Scientists strapped a bat to a swing, pointed the swing at a wall, hooked up some microphones, and let loose. Sure enough, a bat swinging at a wall lowers the pitch of its emitted call. So, bats can compensate for their own movement through space by dropping the pitch of their call, making the pitch of the echo ALREADY ACCOUNT FOR DOPPLER SHIFT BY THE TIME IT GETS BACK TO THE BAT. Totally. Friggin. Badass.
2-The ear and auditory pathway
“Auditory pathway? Ughsheesh. That sounds boring. I don’t want to read about that.” said nobody awesome ever.
Our inner ears are pretty complicated. Without getting stained with details, sound transduction works basically like this:
1) Sounds, which are essentially air pressure waves, vibrate tiny bones in the middle ear that then convert those vibrations into pressure for the inner ear.
2) The basilar membrane, a bendy flap of tissue in the cochlea that looks like an industrial-strength file, vibrates in different spots based on the frequency of these vibrations.
3) The bending basilar membrane causes tiny hair cells adjacent to the cochlea to bend. These hair cells are connected to neurons that can detect when these hair cells bend.
What did we learn here? Basically, pitch matters. Low pitches vibrate different hair cells than high ones. Bats are crazy though. Really crazy. I once saw one bite the head off a human.
Bat basilar membranes, the part of the ear that transduces sounds into nerve impulses, are wider on the part of the cochlea where they detect the frequencies of their echoes. This helps for a number of reasons: 1) It increases the volume of noise in this frequency range, 2) It allows bats to become more sensitive to their own echoes, and 3) it helps reduce sensitivity to their own calls, reducing the odds of confusing those calls (or other sounds) with echoes. It’s also pretty cool to point out that bats contract muscles in their ears when they screech, dampening the sound of their calls further. All in all, bats are pretty much deaf to their own calls but highly sensitive to their echoes. Also, different bats are sensitive to different frequencies, limiting the odds of cross-talk between species.
Left: Bats are sensitive to different frequencies. More hair cells at certain spots along the basilar membrane increase sensitivity. Right: The bat inner ear and auditory pathway.
Alright, this is about to get nuts. I recommend not reading this if you’ve just had a heavy meal, because you may be so amazed that you’ll spew half-digested mush all over your keyboard.
3- The brain
I’m so excited to tell you about bat brains that I’m literally going to get some Oreos. It turns out I was actually excited about the Oreos all along.
The auditory cortex is the part of the brain where auditory information is processed. You and I both have auditory cortexes. This is where information from the ears is organized and sent to other parts of the brain to aid in functions like cerebral processing, speech, and motor function. It’s also the part of the brain that allows us to differentiate between a high E flat played by a piano and a high E flat played by a chainsaw.
Bats have auditory cortexes too. Theirs do many of the same things as ours. But there’s got to be a reason I’ve decided to spend an entire section on their brains. Trust me, there is.
Remember how the cochlea can organize sounds by frequency? We tend to keep nerve impulses of similar frequencies bundled together as we send sound information from our ears to the auditory cortex through various brain structures. So, different parts of the auditory cortex become active when we hear different pitches, giving us somewhat of a tonal map of our sounds. Bats do this too, as do many animals. Here’s the difference: bat brains are capable of producing an ACTUAL map based on sounds.
The bat auditory cortex has two pretty badass regions. One is the FM-FM region. Remember FM pulses? Those are the calls bats use to determine where things are in the space around them. This function is done here. Neurons in the FM-FM area respond to the amount of time in the delay of a call and the harmonics of the call’s echo? What is a harmonic? Click here to find out.
Think of the FM-FM area of the auditory cortex like a 2-D map. Each harmonic excites different horizontal sections from top to bottom, while the left-right axis responds to different delays. So, if the bat detects an echo from the 2nd harmonic after 8ms, neurons in a specific area of the FM-FM area will start firing. Enough of these allow a bat to tell how the large size and distance of the object is.
Bats auditory cortexes can also produce a mental map of sounds based on their velocity. Recall that bats use CF-CF calls to detect the Doppler Shift of sounds and tell whether they’re moving. They process this information in the CF-CF area of the auditory cortex. Like the FM-FM area, certain cells become active when sound properties are just right. Bands of cells respond to certain CF frequencies, and other bands respond to the velocity, or Doppler shift, of the sounds encoded. What bats end up with is a map of awesome.
Left: FM-FM area from the auditory cortex of the mustached bat Pteronotus. Right: CF-CF area.
So what’s the point? Oreos can get me really excited. And to be specific, I’m talking about the golden ones. For some reason the regular Oreos get stuck in my teeth and I can never seem to get them out. Not that regular Oreos aren’t good, I’m just a little bit more partial to the ones that don’t annoy me. And bat brains, those are cool too. I wonder how they make the crème on the inside of the cookie. DO they keep it in big vats? I wonder how much would I have to bribe a guard to swim in that vat for 20 minutes.
Could you imagine if I ended the article that way? Hahahahaha. I am so funny. But seriously, I am actually going to end the article this way. You don’t get a summary of what I said earlier.
Want to suggest a topic for Badass Biology? Want to tell me how awesome a person you think I am? Interested in funding me? I didn’t think so. Anyway, leave a comment below and I might talk to you about stuff.
A big shout-out to “Behavioral Neurobiology” by Thomas Carew for much of the information and figures used in this article. Dr. Carew, if you’re reading this, you seem like a cool guy. Email me and we will go grab a beer and some Oreos.
Here an agar plate was used to culture Serratia marcescens, a Gram-negative bacteria. 
