• Question: How have humans evolved in the past 2 million years? In evolution, this isn't very long, yet we've gotten so far. How?

    Asked by Minecire to Lindsay on 19 May 2015.
    • Photo: K. Lindsay Hunter

      K. Lindsay Hunter answered on 19 May 2015:

      The last two million years has actually seen much of the evolution of our own genus, Homo, so it’s been a very busy time for us!

      From the outside, the most striking differences are a refinement of features, that is, overall, we’ve become more lightly built than our ancestors. Our forehead has become more vertical, our occipital more rounded, and we’ve even developed a chin! As we spread outside Africa, we also started adapting to local environments and climates, so that’s where skin color and body shape comes into play. We finally have what we call anatomically modern humans (AMH) emerging about 200kya. These are people that look a lot like we do today.

      Cognitively, there’s been a LOT happening, though there is disagreement on whether these perceived differences in thinking are of degree or of kind. Whatever their origin, the BEHAVIOR of humans has changed a lot in the last 2 million years, as this saw us first leave Africa, all the way to landing on the moon! We’ve seen the advent of behavioral modernity with art and symbolism, which are largely regarded as the first indicators of spoken language.

      There’s not really a clear idea as to “how” or “why” our evolution has taken this particular path. If I had to guess, though, it’s because we’ve had a steady reduction in most of our senses, which has led us to become ever more reliant on others and their memories to understand and negotiate the environment around us. I think that this reduction in sensory experience, coupled with a socially gregarious evolutionary history has provided the selection pressure necessary for our advances in cognition, including retrospective and prospective memory, as well as symbolic thought and language. These changes in the way we think have effectively helped to balance out that we’re relatively helpless when it comes to exploring the environment with just our own senses, and lets us pool perceptual experience, not just with those around us, but across time and space, allowing for accretional knowledge! As we’ve accumulated more knowledge, we’ve developed new ways to accumulate more (spoken language and storytelling, written language, printing press, digital memory, etc.), and also learned to manipulate our environment. These changes to our environment have had interesting effects on the way we evolve, saving many individuals that would’ve died in the past. It’s said that humans domesticated themselves, and in a way it’s very true. We’ve certainly changed the evolutionary playing field!