Humans are a species that permanently inhabit every continent on the planet. But of course, like all other species, we’ve evolved. So where and when did this take place? Figuring out important temporal and spatial questions related to our own evolution has been one of the central missions for evolutionary anthropology over the past 100-150 years. In order to gain satisfactory answers we had to learn a lot about our closest relatives, our fossilized ancestors, and our own genomes. In the video below I attempt to explain how our understanding of evolution has developed:
The Ancestor's Tale was one of the most important popular science evolutionary biology book I've read. I think it is my favourite Dawkins book. Mostly I enjoyed it because it was such a brilliant idea to explain evolution in the narrative structure that he did. It's a great way to understand speciation and common ancestry.
First of all, well done Cadell and team, the video is engaging both on a content level and visually. Great work. I have a question that may seem silly. If at one point in our not too distant evolutionary past we were comfortable climbing trees and even sleeping in them, why are we now not nearly as comfortable (largely) with heights? Has enough time elapsed, in evolutionary terms, to have eradicated our affinity for heights or am I way off here and I'm of a minority of humans that doesn't feel okay napping in the branches? That said, many people do crave climbing etc, can this be attributed to our evolutionary past? Are there other examples of our now dormant past behaviors that express themselves on a smaller level than they once did? My guess is the answer is "yes there are many" and they're all staring me in the face. What are some of the most prominent and obvious? You know, sort of the behavioral "tail-bone" if you will. A vestigial trait left within me by my tree-dwelling ancestors.
Well, the seeming universal fear of heights is definitely justified. Since the emergence of the genus Homo (2 MILLION years ago) we have been completely terrestrial. The australopithecines all likely exhibited a mixed behavioural repertoire that included a mixture of terrestrial and arboreal living (but most likely lived terrestrially for most of the day before finding a safe place to sleep in the trees at night). I guess the main point is that even for the australopithecines the trees were just a better option than dealing with vicious African predators at night (sort of "pick your poison" - heights or predators - at least with heights you are in more control of the danger). In terms of hominins (all species back to the common ancestor with chimpanzees) I doubt many of them had an affinity for heights. I should suspect that as soon as we start to see habitual bipedalism most hominins opted for a terrestrial over an arboreal niche when the opportunity presented itself. Tough to say, I've never read anything about that. It's entirely possible. I know chimpanzees and bonobos are both very good climbers and seem to enjoy it immensely. Lots of tough questions! Any intense proclivities we have related to sex, sleep, eating, and socializing are all remnants of our evolutionary past. In regards to sex the deep desire to mate guard, or with food our strong affinity for sweet things, with sleeping our particular circadian rhythm tied to the solar cycle, or with socializing our ability to build and maintain large networks. Also physical things like being great long distance runners when compared to almost every other species - that particular trait seems to have evolved about 2 million years ago.why are we now not nearly as comfortable (largely) with heights?
Has enough time elapsed, in evolutionary terms, to have eradicated our affinity for heights
many people do crave climbing etc, can this be attributed to our evolutionary past?
Are there other examples of our now dormant past behaviors that express themselves on a smaller level than they once did?
Some curiosities to add: Falling dreams. Rock-a-bye baby in the tree top. The sensation of falling that jolts me awake even though I wasn’t quite asleep. The relaxed sleeping state of the body that seems to mitigate injury when falling out of bed (though this is anecdotal, so grain of salt and all that). As someone who is not afraid of heights, I only ever get the scared feeling of peering off an edge when I don’t have adequate points of contact to something stable (three is usually enough). Of course, I used to climb to the tops of 20 to 30-foot trees when I was little — and that, I think, is the difference. If we slept in trees, or at the very least had to spend time in precarious places, the fear of heights would be overcome; the brain can learn how to handle it. In fact, because this is such an innate fear — and because it’s a fear, period — I doubt it comes from the human part of the brain, or the primate part, or even the mammal part, but from our lizard brain. I wouldn’t be surprised if a mouse had falling dreams, or an elephant, or a whale, or even birds. Evolution (without agency, mind you) works by pitting contradictory advantages against each other. The curiosity that killed the cat is precisely what enabled the species to survive. Similarly, the overcoming of fear of heights that I believe pervades any brain with a modicum of decision-making was necessary for the survival of many of our ancestors and probably should not be thought of as an innate affinity, but something learned, even if at a very young age. We’d be more comfortable with heights as a species if we had to be.