What Makes Us Human? was a recent episode of Horizon, presented by Alice Roberts while she was pregnant with her second child. So the frame was lots of gooey shots of little babies or shots of Roberts looking pregnant, and the meat of the programme was about some of the things that do or don’t set us apart from our closest relatives in the animal kingdom (chimpanzees, of course!).
One obvious difference between people & chimps is that we’re more intelligent than them. But actually the differences appear to be more subtle than one might expect. Roberts visited some researchers who look at co-operation in chimps & humans. Chimps will co-operate to get a reward, but if the reward is uneven – one gets more or one gets the reward before the other – then the chimps don’t care. Well, the one that loses out does, but not in a way that gets them their “fair” share. But if you do similar experiments with young children (toddler age) then an unequal reward gets shared out. Importantly this only happens if they had to work together to get the reward – co-operating means sharing.
Another difference is the helplessness of a human baby when it arrives on the scene. This is something that has had an “answer” for decades, but recent research has suggested the “answer” isn’t the whole story. Babies are born at the point where they only just fit through their mother’s pelvis, and it has been assumed that there are two selection pressures on the width of the birth canal – one is that wider makes it easier to have bigger headed babies, and the other is that narrower makes walking more energy efficient. So the theory is that women’s pelvises are at the sweet spot between easier childbirth with more developed babies and walking efficiently. But new research is suggesting that women’s walking (and running) is no less energy efficient than men’s despite a difference in gait because of the different shape of pelvis. So that may not be the explanation, you’d think if walking efficiency was the important factor then women’s hips could be wider. The new theory is that women’s metabolisms can’t continue to improve to keep up with the demands of their unborn child – babies are born at the point where their mother can no longer supply all their energy needs. Something about this segment left me with questions about whether there was more data than was explained, because it felt a bit pat & a bit too much jumping to conclusions.
When you look at a human brain & human nerve cells they show more connections (and dendrites) than other animals. Humans have more duplicates of a particular gene to do with dendrites than chimps & if you duplicate this gene in mice then you get more dendrites & connections – in the right proportion to explain the difference between humans & chimps. In this segment Roberts also talked to a scientist who is starting to map, to visually image, actual brains – at the moment he’s just doing mouse brains (very slowly) as they’re small. But eventually the plan is to be able to investigate a human brain this way. They end up with a colour coded three dimensional diagram of all the nerve cells in a brain with connections mapped etc. This looked cool, but I’m not sure how much it actually tells us in the long run – as I understand it brains are all unique in detail, even if similar in general. And does “neuron A connected with neurons B, C, D & E” tell us much about what any of these do?
(And am I cynical about Horizon’s presentation of science because I go in thinking it’ll be shallow, or do I go in thinking it’ll be shallow coz it often leaves me with questions?)
The Royal Institution Christmas Lectures are a series of lectures aimed at children and broadcast on the BBC. I used to watch them every year when I was a kid. We recorded the series in 2011, and have only just got round to watching them – that year they were about brains and the lectures were given by Bruce Hood. The first lecture in the series was titled What’s In Your Head? and covered the basics of what a brain is, how nerves work and the sort of modelling brains do to make sense of the world.
As it’s aimed at children I don’t think it covered anything I didn’t already know, but it did it with style and involved a lot of demonstrations – some of which were rather neat. For instance Hood & another scientist showed that brains work on electricity by disrupting the ability of the other scientist to move his hands properly using in electromagnet against the head. So the chap was clapping and then they switched on the moving magnetic field & he could no longer co-ordinate bringing his hands together. There was also a little bit about MRI scanners to look at brain activity – with a striking visual demonstration of how powerful the magnets involved are: a nurse went into the room with a spanner on a string and then the machine was switched on and the spanner swung up and pulled towards the machine.
Another bit was about how the brain sets up patterns as it learns about the world and how that can lead to being disconcerted by new experiences – like if you eat grapes then your brain learns that round, green, sweet is a pattern associated with grapes. The first time you meet a green olive, you see round and green and then your brain fills in “sweet” because that’s the learnt pattern. So when you eat it you get a nasty surprise. This example particularly stuck in mine & J’s heads coz until recently neither of us ate olives (I’ve somehow acquired a taste for them over the last couple of years) – so the “yack!” reaction he was talking about amused us 🙂