Large brains are energetically expensive, forcing scientists to figure out how our ancestors were able to scrape together the resources needed to develop them.
When you get a moment, check out How a Fly Flies, it's a TED talk by Michael Dickinson that talks about how evolved a fly is. Brain size and function has a lot to do with it. It sure does take a lot of energy to run our brains, hopefully we can use them to keep the Chimp insurgence at bay.Surprisingly, even though we have to fuel a massive thinking organ we don’t use more energy than a chimp; whose piddly little brain is only ¼ the size of ours (which will make it more embarrassing when they take over the world).
First of all, I laughed out loud when I read that.
That is a rather interesting talk. When you look at mammal brains they all have a very similar structure. The human brain, for all intents and purposes, is just an enlarged chimp brain. So it's easy to forget that other groups are just plain freaky in the neuron department.
As a general rule brain size relative to body size is a good predictor of intelligence, although other measures can be better in different lineages. For example, primates have a high neuron density thus absolute brain size is a good predictor of intelligence amongst them. This high neuronal density also means that humans - despite not having the biggest brains - appear to have the most neurons of any animal.
It does seem strange to me to use other animals as a measure of the gut vs. brain hypothesis. Without opposable thumbs and bipedalism, other species might lack a rewarding avenue to take advantage of trading gut for brain. I wonder what the plot looks like for primates?After all, no other species uses fire to prepare their food and we’re the only primate to eat a large quantity of meat.
The main reason they were examining other animals is that a lot of the raw data Aiello and Wheeler based their original hypothesis on came from non-human species. Thus animal data has always played a big role in the expensive tissue hypothesis. Of course, whether animal data can be used to examine humans is a big fat question mark given how different we are. At the same time I'm also weary of special pleading. The "refuting" paper noted that for the expensive tissue hypothesis to remain viable we must propose unique mechanisms operating in humans, which Occam's Razor doesn't like.
Thanks. I can see that. However, I wonder if the study included fish and arachnids? :) At some point a line was drawn based on taxonomical definitions. It seems to me, the question is not whether or not animals sacrifice gut for brain, but whether 'gut for brain' was a niche that humans filled, or if the inverse change of the two was coincidence. It doesn't seem to be possible to answer that question by analogy unless all species included in the data set could explore the niche to begin with. Glad that I'm not an evolutionary biologist. :)At the same time I'm also weary of special pleading. The "refuting" paper noted that for the expensive tissue hypothesis to remain viable we must propose unique mechanisms operating in humans, which Occam's Razor doesn't like.
No, the study only included mammals. However they - and others - note that the expensive tissue hypothesis does seem to be in play in fish (such as the artificial selection study I mentioned in the post; where fish who were "evolved" to have big brains also developed a smaller gut) and a few other groups. Of course, if we're debating over whether or not data from other mammals is applicable to humans then data from fish surely suffers from the same flaws and then some! Last time I checked they didn't have fire either!
I like how evolution almost seems prepared to dispense with an organ if it demands too much energy. We don't need to be technologically advanced and emotionally developed creatures in order to propagate our genes. We just need to be able to live and spread our seed. Strong muscles, high agility, and quick reflexes require less energy than a complex brain, whilst still contributing significantly to the ability of a species to survive. Hence, unless conditions are absolutely ideal, there's little incentive for animals to develop the kind of intelligence that we've developed. I'm not suggesting that humans perhaps aren't meant to be here. But I just think it's fascinating that we're so inconsistent with the rest of nature. We might suppose ourselves the pride and joy of natural selection, but really that's only true insofar as we are capable of surviving longer than other species. Our bodies are so hopelessly adapted to hardship, that once our technological advantage is taken away from us, our prospects become suddenly very bleak. And maybe, if circumstances become extremely difficult to endure, we might just end up losing our big brains, and end up developing big bodies instead.
Strong muscles require food, high agility is expensive, and while quick reflexes are great, what's the point if you can't coordinate them? Humans most significant advantage is our ability to cooperate in an extensive manner, well beyond anything other animals do. Each human exists as a dual being; an individual and a team member, a node and a server. This is an underestimated advantage when most people think about it. Say we are back before civilization. We are hunting Gazelle. I ask you to run ahead; you do so, we've had this hunt before, you usually run ahead. I take off after the Gazelle, ready to push it in to your trap. While you're waiting, you notice a lioness in the grass. You can choose to do a few things here, but the fact that you can make an individual decision, such as to kill that lion, while simultaneously operating within the parameters I set for you is fantastically useful in harsh environments. Large brains let you plan, react, and fight better, and most importantly you learn from mistakes beyond simple responses. If you fight a lion and survive, you will know what not to do in a situation, and can then tell others what not to do. The best advice is not to hit the sharp parts. Humans are also rather naturally talented warriors. Fight something anywhere and the first thing you'll do is pick up a rock. Its instinctive, and we know, without really thinking, how to hold that rock, how to hit best with it, and how to throw it. That's not a technological advantage, its a dude with a rock, and I'd bet on a hunting group of humans with rocks and branches against any other animal walking the planet. Last thing before I sleep, you realize humans are probably the best adapted to harsh climates,right? Sure, if you take away our complicated technologies a good portion of people will die, but that'll happen with any environmental change. Humans have occupied the world in every corner that we could reach. Mountains, tundras, deserts, islands, forests, tropics, swamps, volcanic areas, you know it. I can't think of a species as universal, because unlike say, dogs, or livestock, all of the humans in the different areas are basically the same. Skin color changes, facial structures change, but there's no longer hair, no tail, no super elongated canines, nothing. its a bunch of humans. And we did all of that without a motor to drive us. Hell, most of the human race got to where it was by walking. Sure if you have a lion bite us we get messed up, but put the lion in Siberia and it dies. Humans just make it a coat.
I don't object to your observations. I just think it's important to illustrate that a human brain isn't the pinnacle of evolution, and that the developments of our brain can still be exchanged for other qualities under certain selective pressures. It's true, that having a large brain and a sophisticated intelligence are an immense advantage, and make us exceptionally adaptable. But bacteria are adaptable also, and this isn't contained within their individual intelligence, but within their ability to rapidly proliferate and evolve. Human beings are admirable, but developing advanced intelligence wasn't the inevitable course of a species seeking survival, and I wanted to point that out.