All Ice Age art is mysterious. As the exhibition that has just opened at the British Museum confirms, our distant ancestors were accomplished artists, but what they were trying to achieve with their images (if anything) is far from certain. The publicity for the show says it was ‘40,000 years in the making.’ You’d think that by now we would have some idea what our forebears were up to. But the exhibition doesn’t have any answers. Over the past few years, however, I have been working on a theory that, I think, explains some of the mystery.

The most curious Ice-Age objects of all are the so-called ‘Venus figurines’, small sculptures that can be held in one hand, showing mainly naked women with large breasts, bulbous buttocks, swollen stomachs and distended vulvas – they appear to be pregnant. Some have scratch marks on their thighs, suggesting the breaking of the waters. One has been found in Russia with 28 red spots on her thighs, intimating the menstrual cycle. Often they have no heads or arms, as if these aren’t important, but have a hole bored through the figure in a loop near the top. They were only ever carved, hardly ever painted on cave walls.

They have been found – dated to between 40,000 and 13,000 years ago – in a broad swathe running from the Dordogne region of France through Monruz in Switzerland into Siberia.

The starting point for my new theory is a suggestion made to me some years ago by Randall White, professor of anthropology at New York University, when I was researching my book on the history of ideas.

He observed there must have been a time when ancient men and women had not made the link between sexual intercourse and birth – the interval of nine months being too long. Women would then have seemed exceptionally miraculous creatures, swelling up for no apparent reason, and then producing an infant. No wonder ‘The Great Goddess’ was one of the earliest forms of religion.

With no understanding of the reproductive rhythm, it would have been of paramount importance for people to know when a woman was about to give birth. Not all women swell up to the same degree, or develop pendulous breasts, so other details needed to be recorded, like distended vulvas. The loop that features in many figurines would have been for string to pass through, so it could be a portable ‘aide memoire’ as the hunters roamed after the reindeer.

Parturition is a dangerous time, threatened by predators (the birth of elephants in the bush is still a dangerous time for elephants) and so I believe that hunter-gathers, chasing reindeer (which inhabited Eurasia from France to the Siberian steppes, between the northern limit of the ice sheets and the southern limit of the Pyrenees, Alpine and other mountain ranges), recorded the anatomical details of women nearing birth, so that they knew how to anticipate the event, and could find a safe cave.

Three pieces of evidence indirectly support this:

  • In certain Middle Eastern ancient cultures, women are shown giving birth to bulls. Since no one can have ever seen such a phenomenon, this image probably represents a myth, that woman could be impregnated by spirits. These images die out 13,000 years ago.
  • The latest evidence confirms that dogs were domesticated about 12,000 years ago. Dogs are the large mammals with the shortest gestation period (about 60 days; humans are 285, horses 340). Ancient people may well have conceived the male reproductive role from observation of dogs. Australian evidence underlines this: Aborigines discovered the male role when the dingo was domesticated.
  • Again in ancient Middle Eastern cultures we see a change, around 13,000-11,000 years ago, from communal burial to more familial burial pattern, individuals being buried under their houses, not in communal graves; and we see more ancestor worship. With the discovery of the paternal role, families and specific ancestors became more important.

The story doesn’t end there. In Genesis, in the Bible, Adam and Eve both eat from the Tree of Knowledge, after which they discover they are ‘naked’. This is incomprehensible unless we accept what the distinguished biblical scholar Elaine Pagels says, that knowledge and nakedness refer to sexual awareness in some form (as in ‘he knew his wife’).

On this account then, the bible records a momentous event in our biological – and not theological – history: recognition of paternity. Hunter gatherers are notoriously polygynous. It was now, 12,000 or so years ago, that, as Elaine Pagels also says, marriage becomes monogamous and ‘indissoluble.’

It sounds very counter-intuitive, for the male role in reproduction to be discovered so late. What did early people think they were doing when they were having sex? Well, what do animals think they are doing then they have sex? I published the hardback edition of my book a year ago and now, at the time of the paperback, no one has come out of the woodwork, to shout me down. The British Museum exhibition is being reported all over the world. Now is a good time to study these figurines afresh, to see whether the new theory holds up.

The Times, first published February 2013