Human evolution 101

This is not a blog for Paleoanthropologists to talk to each other. We have scientific journals and conferences for that. And although I hope they stop by and share their feedback on ways to make this blog better, this is a blog for anyone who is curious about human evolution, ancient human species, and especially my favorite – Neandertals. I am a graduate student, earning my master’s degree in paleoanthropology from California State University, Northridge (see the About page for more on my background). I’m not an expert – yet – but I’m excited to share what I’ve learned already. So I thought that while I’m on my very first excavation here in Saint-Cesaire, France, I’d spend a few blog posts clearing up some confusion and misunderstandings I’ve come across when it comes to Neandertals and human evolution. Let’s start with some basics.

Vocabulary Terms

Paleoanthropology – the study of ancient humans and human evolution.
paleo = ancient / anthro = humans / ology = study of

Hominin — the name that refers to all the species that make up the branches of our family tree, or more accurately our crazy family bush covered with creeping vines and sprawling roots, and even some weird flowers and fruit, and includes Homo sapiens (you and me!) as well as the bipedal but small-brained Ardipithecus, and the modern and ancient great apes.

Homo – a sub-group of hominins, that includes the species with Homo in their name. These species look more like us and does not include the great apes. Let’s say these are our first cousins, while Hominins include our immediate family, our first cousins, second cousins, and even our third and fourth cousins three times removed.

One of the most common and recognizable memes in our times is the evolution one – you can see it here, and I promise you it is the only time it will appear in this blog. This line of ape-like to human-like fihuman-evolution-david-giffordgures walking across the page from left to right, gradually standing up straighter and walking upright –paleoanthropologists and evolutionary biologists hate this meme. There are so many things wrong with it, I’m not even sure where to start. Evolution is not a straight line, it is not gradual, and it is not naturally “progressive” (meaning increasingly more complex or sophisticated). Should I even bother to mention that it is also culturally bound? It betrays its Western origins by reading from left to right, and it is unambiguously male (always depicted with males, and sometimes even including stereotypically male weapons or tools), and often, like this one, it even goes from black to brown to white. Ugh, really? (UPDATE: My friend James Dignan pointed me to Carl Sagan’s wonderful video about human evolution that ends with a human woman. Of course! Because Carl Sagan is awesome! Who doesn’t love him? If you don’t, well then, I don’t know what to say besides go watch all of Cosmos right now. Just go do it.) Besides all of the problems with this meme, this over-simplification is not just scientifically inaccurate, it’s BORING! Evolution in general and human evolution in particular is way, way more interesting than that. It is full of surprises, “mistakes” and dead ends. It is a huge, complicated, messy jumble, and scientists can spend their whole careers trying to untangle just one thread of it. So can we get rid of this awful meme please? I mean I get it, it is visually appealing, memorable, and clearly conveys a concept – all things memes are supposed to do. But can we try and come up with something more representative of reality? Post your ideas in the comments, please! Maybe we can create something better.

So what does evolution mean then? Well actually evolution only means change over time. In that sense of the word, your iPhone evolves. But most people mean natural selection when they talk about evolution. Natural selection is a concept made famous by Charles Darwin (although several thinkers had already been moving in this direction when he published On the Origin of Species in 1859, and another “naturalist,” as they were called at the time, Alfred Russel Wallace had written basically the same book at the same time. Darwin just published his first. History is a bitch sometimes.) Here is the definition, are you ready?

Natural selection is the process by which biological traits that are passed down from one generation to the next become either more or less common as a result of whether these traits increase or decrease the individual’s reproductive success. So for example, if a bird with a differently shaped beak is better able to eat hard Darwin's_finches_by_Gouldseeds when other food becomes unavailable during a drought, then this bird will live long enough to produce offspring that inherit that shape of beak and can in turn have a better chance of surviving future droughts. The phrase “survival of the fittest” is one that frequently frustrates paleoanthropologists and evolutionary biologists. Because although it is completely correct and accurate, it is terribly misunderstood and misused, so many avoid using it altogether. Modern usage of “fit” and “fitness” as meaning able-bodied, strong and powerful is partly to blame, I think. (I don’t have the space or desire to get into the troublesome social Darwinism or creationism and their contributions to the misunderstanding in this post.) But “fitness” in this sense means “fitness” to the environment. So quite contrary to images of meanest and strongest, the fittest animal could be the smallest or quietest or brownest (less obvious to predators). It could mean the animal who is most cooperative with its social group, making it better able to find food and defend itself. While images of a ruthless uncaring nature may make some people uneasy about the concept of natural selection, the success of a species can mean the most successful members are those who are most compassionate and patient. Raising a helpless infant (human infants are particularly so) requires both of these qualities. And showing compassion to members of the social group, who are also kin, not only perpetuates your own genes, but also earns you help and compassion when you are hurt or sick. When there is no way to preserve food, giving away meat you kill (no one person or immediate family can eat an entire animal at once) is insurance that you will get meat in the future when you are not successful in the hunt. Food sharing is a very important part of our evolution as humans. In fact I’d say that after bipedality, it was probably the next most important step in our evolution.

Speaking of bipedality, that is one important thing that irritating meme gets wrong. Bipedality, the ability to walk upright on two legs, is not exclusive to humans. Just take a look at birds (who evolved from dinosaurs), kangaroos, and even some lizards when they run. We humans are primates — along with apes, monkeys, chimpanzees, orangutans — and primates possess various degrees of bipedality. Some primates are knuckle-walkers (you can guess what that means) and some walk on two legs for short distances. Look closely, though, at how non-human primates walk, and you can see a clear difference. Put simply, modern humans are expert walkers. Our bodies are designed for long distance walking and running. Our spine, pelvis, knees, and feet have all evolved to make standing and walking our particular “thing.”

Hominins were mostly bipedal by 6 million years ago, and full-time bipeds by about 2 million years ago. (One of my favorite pieces of evidence of bipedality is the Laetoli footprints, which are 3.7 million years old. I love these footprints so much sometimes I daydream about the Hominins who made them.) Bipedality afforded many evolutionary advantages. We have evolved to become a very visual species (compared to dogs, for example, who get much more information with their noses). Standing up meant we could see much further, to find food and watch for predators. It also freed up our hands for many things, not the least of which was tool making, although that came a bit later (but according to an exciting new finding, apparently not all that much later). Losing our body hair and growing our brains (Ardi, as clever as the species undoubtedly was, had a very small brain) came much later.

So who were the Neandertals, exactly, and why should we care? Well, I couldn’t help spending this entire post on human evolution in general (we needed to get that out of the way first), so I’ll save Neandertals for my next post. But what makes them so interesting to me, why I am here at Saint-Cesaire helping to look for more clues about them, is that they are the most recent extinct species of Homo. They are so close to us, yet they are not us. They evolved separately, in isolation, so what can that tell us? That evolution always follows similar paths? Maybe, maybe not. But we can’t help asking because, well, that’s what humans do.

You may ask yourself – well, how did I get here?

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2 Responses to Human evolution 101

  1. Pingback: What Happens When You Assume | Paleocentric

  2. Pingback: All That Death: the Reality of Studying Human Evolution | Paleocentric

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