“It’s a different way of looking at human evolution,” says anthropologist Dr Alice Roberts of her new three-parter Origins of Us. “I’m doing it by looking at us today and asking: what is it that makes us human?”
The series (starting 9pm 17 October BBC2) illustrates that everything you need to know about human evolution is right there in your own body. Congratulations! Your prominent forehead, small teeth and flexible spine – giving you the power to think, cook and run – make you a member of Earth’s most advanced species. “I’m being unashamedly parochial and saying, we are special,” says Roberts.
The starting point is the last ancestor we share with other primates: the chimpanzee of 6-7 million years ago. “Everything that happened after that is what made us unique.” So Origins of Us takes Roberts to Africa to see our closest relative, the modern chimpanzee. “In the forest of Kibale in Uganda there are a huge number of chimps who are completely habituated to humans looking at them. They ignore you, walk straight past you. They’re quite happy for you to film, it’s very strange and quite scary. They glance nonchalantly.”
Elsewhere in Africa are humans who provide a different view of our past. The Hazda of Tanzania are “one of the last hunter-gatherer groups in the world. Hunting and gathering has shaped our bodies, our life expectancy, but also our psyches and societies. It’s likely that monogamy emerged in a hunter-gatherer society – it makes sense to share food in that way and to have someone who will look after you and your children.
“There’s a fantastic bit of research looking at risk-taking as a way of showing off to women, which has its roots in hunter-gatherer days – you’re likely to be a better hunter if you take more risks. Hazda women want to pair up with a good hunter. In our society today, men do quite odd things to impress women. The research analysed skateboarders – the level of risk taken when performing tricks when an attractive woman was watching went up.”
Roberts has presented programmes on everything from Shakespeare to swimming, but is on her specialist ground here. She’s keen to emphasise the role the latest science plays in the series. “It’s not just me wandering around a landscape waving my arms – I’ve gone to meet the people doing the research, some of which hasn’t even been published. Some of the ideas haven’t changed much in the last ten years but there have been some really significant discoveries – we are focusing on the newest insights. It’s absolutely on the cutting edge.”
Of course, for an extreme but vocal minority, the fundamental subject matter of Origins of Us will be an affront. The theory of evolution is unproven, downright false or even blasphemous, they’ll say. How does it feel to be someone like Roberts, who’s studied a subject in detail for years, only to be regularly told that it’s all bunk?
“It’s not as bad in this country as it is in the States,” she says, “but I’m slightly worried that it might be getting worse. In the States, a number of people won’t accept evolution because they have another belief which stands in opposition to it. I don’t see any conflict about believing in evolution and being religious. If you take the word of the Bible as absolute truth, you are going to start getting into difficulty, but there’s nothing about evolution to say that God doesn’t exist, or that he does. I don’t think people should feel that they have to choose.”
What about people who try to take a scientific line, and say that evolution isn’t “proven”? “If you’re a rational person who wants to understand how the world works,” Roberts replies, “science is the best tool we’ve got. Evolution is only a theory, but look at the philosophy of science: all of it is a theory, but it’s based on evidence. We try to disprove our hypothesis and, if you can’t disprove it based on the evidence around, you take that as the best explanation. I can’t think of any scientists who don’t agree that evolution is the best explanation for all the life on Earth today.
“You have to come up with extraordinary explanations for how all this evidence has ended up where it is if you don’t want to explain it through evolution,” she goes on. “We’ve got so many human fossil species showing all these adaptations accumulating over time – about 20 different hominid species showing a very nice sequence that we fit into. And we see evolution happening in front of our very eyes: we know viruses and bacteria are changing. TB developed resistance to the antibiotics we try to use to kill it off. How is it doing that? It’s evolving!”
So what is it that some people find so hard? Is there some sort of psychological barrier that stops people accepting the science? “It’s a difficult concept to get your head around if you think about it in terms of human lives. We’re so stuck in our own time frame. A thousand years is about as much as you can hold in your head. Once you start talking about thousands, tens of thousands, millions of years, you lose that visceral grasp. But the joy of science is allowing us to grasp concepts that go far beyond the world around us, to reach into deep time and find those answers.”
How about people who feel that even behind something as scientifically well mapped-out as evolution – particularly something like that, perhaps – there has to be something else? A creator? “Who made it happen? Part of the mentality that’s made humans very successful is to have a cause for everything, to have answers for why something is happening. But there isn’t an answer here.”
Finally, there’s a silly but enduringly popular question: if we evolved from monkeys, why are there still monkeys? “Why shouldn’t other monkeys have survived because an odd little group of them have evolved [into humans]? They’ve evolved too. It’s a common misconception that we’ve evolved from chimpanzees – we’ve both evolved from a common ancestor. Yes, that common ancestor probably looked a lot more like chimps than humans, so chimps probably look more like their predecessors. But they’ve done very well, thank you!”
So what evidence is there in our own bodies? Much of our superiority comes from our bipedalism: remaining upright, our knuckles nowhere near the floor. Locking knees enable standing for extended periods, while a wide pelvis, strong neck, low shoulders and long, flexible spine all facilitate speedy, stable running. Long femurs set us further apart: “It’s what really makes us look different to other apes. Having long legs means you have a very efficient pendulum movement when you’re striding out across the African savannah.”
Staying on our feet all day is the key, so it shouldn’t be too upsetting that we can’t peel a banana with them any more. “We’ve lost much of the grasping ability in our feet,” says Roberts. “Our big toe has lined up with all the other toes rather than sticking out like a thumb. But our feet have become very sprung. Get out of the bath and walk across the floor. You don’t get the imprint of the whole of your foot. If chimpanzees did that, the whole foot would slap down. That sprung shape means you get a little bit of energy back every time you put your foot down.
“Evolution doesn’t get rid of things because they’re not useful. It wouldn’t get rid of that grasping ability unless it had to.”
What else puts us on top? Long thumbs, for one. “Our thumbs have got bigger and longer. Interesting new research suggests this isn’t to do with making tools, it’s to do with using tools,” Roberts explains. “You use your thumbs more when you’re holding a stone tool and using it than you do when you’re making it. That shows the human body has adapted to things that we’ve done rather than just the environment.”
But while thumbs and femurs have got longer, something else has shrunk… teeth. “Look at chimps and gorillas: our teeth are minuscule in comparison. There’s a persuasive new theory on this which is all about cooking. Teeth got smaller as we started eating a softer diet. As well as eating a wider variety of foods, cooking allowed our ancestors to get more energy out of food. Cooking starts the digestive process outside your body: even if you get all the calories from raw food, you’re putting energy into chewing and digesting. And you can use cooked food to wean your children more quickly. That means you can stop breastfeeding and have another baby. That’ll help you be more successful as a species.”