The Origin of Our Species

The Origin of Our Species – review

Author – Chris Stringer

Publisher – Penguin

Date – 2011

Stars – 4.5/5

Review

Although I have said this blog is mainly intended for crime and mystery, I have a secondary interest in science and particularly genetics.  Hence, the story of human evolution and how we came to dominant the planet and spread to each and every corner fascinates me.  Chris Stringer is a Professor at the Natural History Museum and Archaeologist by background.  He is eminent in the field of human evolution and his work “The Origin of Our Species” is an effort to summarise his research and that of his colleagues so that the general public can have some understanding of our roots.

Even the reader with little science knowledge can appreciate the effort that has gone into the work and it is well written making some of the more complex concepts understandable.  The author takes us through the timeline of archaic humans, the eldest being Homo Erectus (~1-2 000 000 years) and, of course, the most recent Homo Sapiens (~200 000 years).  Before the occurrence of the Homo genus, other pre-human primates such as the Australopithecines, are discussed and make for remarkable reading.  The later species in between Erectus and ourselves, such as Homo Hiedelbergensis, Home Ergaster and Homo Neanderthalensis are less well established in terms of the timing of their existence and whether the world was co-inhabited by multiple human species at any one time.  For the Neanderthals however, the evidence is compelling for co-existence and, indeed, some degree of hybridisation.

The main theme of the book however is human migration and dispersal.  How did we populate the planet and when did this occur.  Stringer discusses a combination of genetic and archaeological arguments for this.  The two main competing theories seem to be a Recent Out of Africa dispersal and Multiregionalism (whereby archaic humans such as Erectus had already dispersed from Africa and went on to founder each individual population).  Stringer makes strong arguments in favour of the Out of Africa model and dispels some of the thought processing behind multiregionalism. 

I think the most compelling argument for the Out of Africa model is mitochondrial Eve.  For those readers unaware, mitochondria are power houses in all cells.  They actually contain their own genetic code which doesn’t get swapped around in a process called recombination during the production of sperm and eggs.  At fertilisation, it is only the egg the carries mitochondria and hence it is only inherited from the mother. For these reasons, any chances that occur in mitochondrial DNA are down to spontaneous mutation and this can actually be time.  For a given length of DNA, there is a specific number of mutations per unit time (years or millennia etc) that will occur.  By comparing the mutations in my mitochondria to those in someone else’s, we can make an estimate as to how related we are and when our most recent common (female) ancestor would have existed.  Now if we take samples from thousands of individuals from around the world, we can collate them into groups – those with fewer mutations are more related and those with more are more distant relatives.  When this is combined with geographical data, the result is astounding.  There many many more groups of mitochondrial DNA in Africa than anywhere else and the number of groups gets less and less the further from Africa – with some places like Australia having only one or two mitochondrial populations.  In essence, this proves that there is more genetic variation in African people than anyone else and hence we can infer that humans have lived in Africa much longer than anywhere else.  The fact that there are fewer mitochondrial populations in other places suggests a bottleneck whereby only a few individuals who left Africa went on to populate the rest of the world.

Stringer summarises this very well, much better than I could.  He does not completely discount other theories, which I think is important in science.  He lends some attention to multiregionalism but gives good reason why this theory is not as strong. For those interested in human evolution, where we came from and where we are going, this is a good introductory text.  He explains a lot about our understanding of archaic human culture, dispels myths about Neanderthal brutishness and provides plenty of images to help the reader conceptualise this complex field.

Apologies if this was an unsolicited review but, having just finished the book, I thought writing about it was a good idea. This helps me consolidate the ideas that I have read.