Pebble Wielding Biped

In 5th grade I was told that thumbs are what separated us from apes. Then in 7th grade I remember learning that it was really the combination of thumbs and intelligence. By The time I was a senior in high school I learned the difference between correlation, and cause-and-effect. This was about the time it was pointed out that apes can use sign language, many primates use tools, and all have mostly opposable thumbs that allow them to manage some fairly intricate digital manipulation (that would be 'digital' as in 'fingers', see below). That of course simply promoted my skepticism that anybody really knew what made humans stick out of the primate pack. As a freshman in college, some history classes and an anthropology class eluded to the possibility that it was the ability to have written language and the use of symbols that separated us from "them". But this wasn't consistent with anything, really... sure we write stuff down in symbols, chimps don't. So what. I didn't see any cause-effect associated with this... it felt more like an artifact of something else. As it turns out, humans as a separate species split long before there was any evidence of using written language.

Finally as a Junior in college--having then taken a lot of archeology, evolutionary biology, sociobiology and anthropology, and being a biochemistry major--I was in a advanced archaeology class that was focused on early African humanoids and evidence of climate change during that same period. There it was. The models popular with people in the field of the evolutionary biology with respect to humans was this: The first humanoids became biologically isolated when they developed the ability to get around on two legs. First, why would this cause a biological rift? Several reasons. First, by being able to move long distances without requiring hands, hands were free to do other things simultaneously such as wielding tools, weapons, and carrying cargo. The other is simple locomotion physics.... the great apes which are our closest relatives, can't move fast or far on flat ground... trees are preferred. This means that the ability to travel more efficiently in tree-less terrain opens up opportunities to access areas not easily accessed by others competing for the same resources. Then there is a more speculative aspect I find interesting: Our big brains? The ability to stand around upright actually increases the "maximum manageable skull size" for our frame. In other words, when your toodling around on all fours, your back has to support your head as a cantilever, and so big isn't so good. It also becomes harder to manage a large skull when swinging around in trees (easier to break one's neck). Big headed apes and monkeys were disadvantaged, but upright standing humans could support fairly large skulls without being disadvantaged, allowing a type of diversity previously being constrained by forest living.

Now, the final question is what actually caused the split? In other words, enabling diversity doesn't necessarily spawn new species. Usually it takes something called selection pressure, some change in the environment that forces a certain unique group to have an advantage over the larger population. That event that triggered the split, as it turns out, appears to be massive deforestation by way of drought, in africa. One could say that deforestation is actually what gave bipedal apes an advantage, and thus our own little branch (no pun intended) in evolutionary biology. In other words: the dissapearance of rain forrest gave rise to humanity (and no, this is not just my interpretation... its a fairly widely accepted theory in the field of evolutionary biology). I hope the irony in this is obvious.


So why am I rambling about this here? Well... up till about two years ago this was all just textbooks, papers, academic studies etc. Now I have a daughter. I have watched her go from this worm-maggot type critter that mostly just cried and pooped, to a "little girl" (she's ~20 months old). The point that she transitioned to a "little girl" from a "baby" was fairly clear: When she started walking. If you ever watch a person grow up, you can see it. The second that mobility can occur with the free use of ones hands, they start acting "like a person". It's uncanny. I am still in awe that it took people hundreds of years to figure out that what makes us so special is the ability to walk around on two feet. I guess hindsight is 20-20.
The reason I bring this up now is because in the last month or so, my daughter has been thoroughly fascinated with rocks, sticks, and wielding random objects found in the playground, all while I am watching with fascination at her pure joy of this capacity to behave in a way that truly makes her human.

Peace.

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