A single woman, the ancestor of us all.
Eve?
Well, that was the story that the media latched on to, and you can see why. However, it doesn't hang together. The occurrence of just one mitochondrial DNA sequence doesn't mean that there was just one woman with that sequence, or that she was the ancestress of all the other women whose DNA was sequenced. Evidence based on the current diversity of various genes shows that there were at least 50,000 women in the human population 70,000 years ago, and many of them will have had that particular DNA sequence, or one that cannot be distinguished from it with the evidence remaining today. The lineages of the women who did not have that sequence continued for some time, but eventually died out: their 'branch' of the human family tree doesn't reach all the way to the present day. We can't be certain why those lineages died out, but in mathematical models such effects are commonplace. Perhaps the women carrying sequences like today's sole survivor were more 'fit', or they simply came to outnumber the others by chance. It is even possible that the choice of the contemporary women to test was in some way biased, and that more than one mitochondrial DNA sequence is actually present in today's women.
How do we know that there were at least 100,000 humans 70,000 years ago, and not, as in the stories, just two 6,000 years ago? Many (about 30 per cent) of the genes in the cell nucleus have several versions in today's human population. Like most 'wild' populations (not bred in the laboratory or for dog shows), each individual human has two versions of about 10 per cent of his or her genes, different versions received from father and mother in sperm and egg. Humans have roughly 30,000 genes, of which about 3,000 will be represented by two versions in the average person. For some genes, notably those of the immune system that give each of us a very specific lock-and-key individuality, making us susceptible to some ailments but resistant to others, there are hundreds of versions of each gene (of four important ones, anyway). The (common)
chimpanzee has a set of these immune variants that is very like the human: in one list of 65 variants of one immune gene, only two were not exactly the same. We don't know about the DNA of enough bonobos yet to see if the story is the same for them, but the smart money says that it will be, possibly even more so. The gorilla set seems to be a little different again (but only about thirty gorillas have been tested).
At any rate, all of these immune gene variants had to come out of Africa in that 'bottleneck'
population that produced all the ex-African human populations. It is unreasonable to suppose that each individual inherited different versions of each variable gene from their parents: some will have carried only one version, the same from both parents, and no one can have carried more than two. The humans that came out of Africa have about 500 immune variants, at least, in common with chimpanzees, out of about 750 possibilities. The humans who stayed in Africa have more: they weren't subject to the bottleneck. There are many other genes where several ancient versions (ancient because they're common to us, chimpanzees, perhaps gorillas, maybe other species) have come through; 100,000 people is a reasonable minimum to carry all those. If you want to be critical and get that number down a bit, you could argue that a few variants from African populations may have been mixed in later, for example via slavery to the US, or to Mediterranean peoples and then via Phoenician sailors to the rest of us. Still, the evidence does not point to an Adam and an Eve, unless they came with a lot of servants, slaves or concubines.
The Biblical stories don't mention those.39
THE SHELLFISH SCENE
The wizards watched carefully.
'There's five of them sitting there with him now.' said Ponder. 'And some children. He seems to be getting on well enough.'
'They're very interested in his hat,' said the Dean. 'A pointy hat always commands respect in any culture,' said Ridcully. 'Then why have several of them tried to eat it?' said the Lecturer in Indefinite Studies.
'At least they don't appear to be warlike,' said Ponder. 'Let's go and introduce ourselves, shall we?'
And, again, when the wizards arrived at the little group around the fire there was the strange sensation of ... nothing. No surprise, no shock. The heavy people treated them as if they'd just returned from the bar; their curiosity level extended perhaps to the flavour of crisps they'd brought back, but no further.
'Friendly souls, ain't they?' said Ridcully. 'Which one's the boss?' Rincewind looked up, and then turned and snatched his hat from a big fist.
None of them,' he snapped. 'Stop pinching the sequins!'
'Have you mastered their language?'
'I can't! They don't have one! It's all point and kick! That's my hat, thank you so very very!'
'We watched you walking around,' said Ponder. 'Surely you've learned something?'
'Oh, yes,' said Rincewind. 'Follow me, and I'll show you - give me my hat'
Holding his sequin-stripped hat firmly on his head with both hands, he led the wizards to a big lagoon on the other side of the village. An arm of the river flowed through it; the water was crystal clear.
'See the shells?' said Rincewind, pointing to a large heap a little way from the beach.
'Freshwater mussels,' said Ridcully. 'Very nutritious. Well?'
'It's a big heap, right?'
'And?' said Ridcully. 'I'm quite fond of mussels myself.'
'You see that hill further along the bank? The one covered in grass? And the one behind that, with all the shrubs and trees? And the -well, see how the whole area is a lot higher than rest of the land around here? If you want to know why, just kick the soil away. It's mussel shells all the way down! These people have been here for thousands and thousands of years!'
The tiny clan had followed them and were watching with the uncomprehending interest that was their ground-state expression. Several of them waded in after mussels.
'That's a lot of shellfish,' said the Dean. 'Obviously not a taboo animal.'
'Yes, and that's surprising because frankly these people seem related to them,' said Rincewind wearily. 'Their stone tools are frankly rubbish and they can't build huts and they can't even make fire.'
'But we saw a—'
'Yes. They've got fire. They wait for lightning to strike a tree or set fire to grass,' said Rincewind.
'Then they just keep it going for years and years. Believe me, it took a lot of grunting and pointing to work that one out. And they have no idea about art. I mean, you know, pictures? I drew a picture of a cow in the dirt and they seemed puzzled. 1 really think they were just seeing ... well, lines. Just lines.'
'Perhaps you're not very good at cow pictures?' said Ridcully.
'Look around,' said Rincewind. 'No beads, no face paint, no decoration. You don't have to be very advanced to knock out a bear claw necklace. Even people who live in caves know how to draw. Ever seen those caves up in Ubergigle? Buffaloes and mammoths as far as the eye can see.'
'I must say you've seemed to strike up a rapport with them very quickly, Rincewind,' said Ponder.
'Well, I've always been good at understanding other people enough to get an inkling of when to start running,' said Rincewind.
'You don't always have to run, do you?'