Paleodyssey

If you’re going to think about homo sapiens in evolutionary terms, it’s valuable to compare the ways in which humans differ from other animals. It seems to me that, even aside from behavioral oddities such as building giant civilizations and tweeting about the Kardashians, we are stranger than platypi. That’s easy to miss, because we think of ourselves as normal. Hah!

Here are a few of the ways that we are weirdos:

1. Humans have huge freaking brains. Brains are useful things; most critters have them. But ours are gigantic. That’s weird because there are definite disadvantages to having so much neural tissue wadded up at the tops of our bodies. First, the metabolism thing. Brains use lots more energy, ounce for ounce, than most other tissue. For that reason, we need to eat more than other animals our size. When we experience metabolic impairments like famine, we must let other tissues go to waste in order to keep greedy brain tissue going so that we don’t die. Another problem is that the size of our brains requires a big head. Look at a baby some time. They seem like they are half head! When we are born, our big honkin’ heads need to fit through our mother’s pelvis, which they barely do. Human men (including me) are attracted to women with narrow waists and wide hips, because those women will be more likely to survive childbirth. Other animals, including apes, find giving birth to be no big deal, something they may nap through. Not so for wild humans, who have incredibly difficult, painful births and high rates of death for mothers and children in childbirth.
2. We walk upright, and we do it pretty well. Can you think of another critter that does that? Some animals, such as bears, are mainly quadrupeds but can get up on two legs for a better view and sort of waddle slowly around, then go back down on their forelegs when they need to make speed. Other animals, such as penguins, walk upright poorly and are optimized for swimming. Apes can walk bowlegged on two legs, clumsily, and knuckle walk for speed.  Two-legged fast movers like therapods and ostriches have a T body configuration, with most of the body balanced horizontally on two legs. The human ability to stand, walk, and run fully upright (far better than what we can do on all fours) is very strange. If we didn’t do it every day, it would be perfectly reasonable to think that upright walking is not really possible.
3. Human females are strange (yes, I know I’m not the first human male to remark on that). First is the concealed ovulation. The females of other species, including our ape cousins, generally go into heat when they are fertile. Males and females actively engage in mating and sex when females are fertile and don’t get horny when those behaviors will not produce offspring. There are mechanisms in place to signal when a female is fertile and when she is not. By contrast, human females seem designed to prevent detection of fertility (and thwart use of the rhythm method of birth control). Thus, we tend to want to have sex all the time, whether it will result in procreation or not. This is utterly strange and biology has no good explanation for it (there are lots of theories, none of them all that convincing). All other species have evolved not to waste energy, time, and precious bodily fluids on sex when there is no chance of producing offspring. We are the only ones whose biology lets us do it for fun. There is also the matter of breasts. There is no obvious reason why breasts enlarge when girls enter puberty. Milk glands are not that big (breast tissue is mostly fat), and other mammals have no need for the enlarged teats that many (not all) human females exhibit. David Brin thinks that breasts and other adult sexually dimorphic characteristics may have the evolutionary purpose of encouraging human males to imprint sexually on adult females rather than children. That’s the least stupid-sounding theory I’ve read. Whatever the cause, I am in favor of breasts, and human females in general.
4. Those in the paleo community like to argue about the meaning of the human eating/digestive apparatus. By comparison to other creatures, we have weak little baby teeth, pathetic for killing or chewing. Compared to our ape relatives, we have short guts that have little plant fermentation capability. However, our guts are not quite built for carnivory, either. However, by comparison to other oddities, our guts seem a paragon of normality.

I’m sure a physical anthropologist could list a few more bits of strangeness (and perhaps correct a few errors on my part), but this is a good start. We are freaky-deaky critters.