Human Evolution, an Ongoing Story


Over at Scientific American, Kate Wong compiled a list of some of the most compelling discoveries in human evolution from 2013. I won’t rehash her entire list here, but the ones that will stick with me for a while include the variation found among the Dmanisi hominins, probably all within the same species. The other is the genetic evidence for interbreeding between Neanderthals, Denisovans, and other extinct humans. Fascinating.

These things also acts as reminders that science doesn’t stand still. This also makes me empathetic and excited for students of human evolution today. The picture is fuller, but also perhaps a bit more difficult to grasp, compared to the days when I was an undergraduate. There were fewer specimens available then, and the the genetic evidence just wasn’t there. At that time, there were no hobbits, or Denisovans, Orrorin, Sahelanthropus, or sediba. Ardipithecus was only recently being understood. I sometimes joke with students that the exams on human evolution I had to take were necessarily simpler than the ones they do. They nod in agreement (of course we know more now than we did then!). But they also groan at all the funny sounding names that seem so unwieldy upon first encounter. 

It’s also a reminder that science has to accommodate new evidence, and often that means that past interpretations were wrong, or at least in need of edification. To some, that means inconsistency, which is often seen in a negative light (“But earlier you said ‘XYZ.’ Now, you’re saying something else!”) That’s the wrong way to see things. Months ago, Holly Dunsworth wrote that it’s bad science to fall in love with your hypothesis, and I agree. With regard to human evolution, in an essay written for the BBC (“Human Evolution, from Tree to Braid”), Clive Finlayson stated that each new finding is potentially revolutionary since it is still a relatively young field:

 

 “It seems that almost every other discovery in palaeoanthropology is reported as a surprise. I wonder when the penny will drop: when we have five pieces of a 5,000-piece jigsaw puzzle, every new bit that we add is likely to change the picture.”

 

I still say that that this is where a scientific approach shines. At a fundamental level, what science has going for it is the recognition that all conclusions are tentative and contingent upon future discoveries that could potentially overturn what we know today. We need to be prepared to change our minds should new evidence arise. That’s often easier said than done, but the principle still stands. When the economist John Maynard Keynes was once criticized for being inconsistent, he replied, “When my information changes, I alter my conclusions. What do you do, sir?” Stubbornness and blind adherence to one’s cherished beliefs are nothing to be admired when they are unwarranted.

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