So we have renewed confirmation that every human being alive today is descended from a single mother, who lived 200,000 years ago. Hallo, cousins!
The lady in question is known as mitochondrial Eve. The name comes from examining the mitochondria which are the energy factories in each human cell. Conveniently they are only inherited through the female line, and have 37 genes which rarely change. In addition they have a variable region which changes fast enough and regularly enough to time the small genetic variations which do occur.
These observations need to be matched against genetic models which use different sets of assumptions about migration, and expansion, and take into account random growth and extinction. In this study, published in the journal Theoretical Population Biology, ten different models were studied side by side – making the result the most robust and reliable to date.
Of course the genetic identification of a single ancestor does not mean that we have discovered the first woman. We know nothing about her predecessors, and it is generally thought that a number of small human populations lived in different habitats before dying out. It would appear that mitochondrial Eve mothered the only line which happened to survive.
An interesting thought strikes me. Traditional moralists have argued that there are certain extreme circumstances in which polygamy would not be forbidden by the natural law. But polyandry is always forbidden. However, in the case of mitochondrial Eve, polyandry would certainly be beneficial in order to achieve more general genetic diversity. Indeed if there were only one woman around – and several males, polyandry would be almost inevitable. Perhaps polyandry was simply too unthinkable for the male moral theologian.
Of course this is small beer compared with a new fossil discovery, published in Nature Geoscience (also on August 17). These take us back 650 million years, and are the earliest evidence of animal body forms, somewhat like a primitive sponge – 70 million years earlier than previous evidence.
Perhaps they are our ancestors too – but this might be harder to demonstrate.