Who We Are and How We Got Here by David Reich - a book review


'Who We Are and How We Got Here' by David Reich is a fascinating book about the study of ancient DNA from old or archaeological bone samples and its correlation to the human species and their migration across the globe in the past. This article gives a quick summary and brief review of the book.

Introduction

The Indian edition of this fascinating book was published by the Oxford University Press in the year 2018. This book has compiled the research work of last few decades done in the area of study of the patterns of genome (complete set of genes) in the human biological cells and then tracing it back to the geographical area in the world from where our far back ancestors dwelled and then moved to other places on the Earth. It is, in fact, a great study in the genealogy and anthropology and gives insight as to where the first post-Neanderthal men evolved from the Neanderthals and how they migrated or moved to other parts of the world. The inferences are based on the subtle changes in the sequence of DNA in the genome in a large number of the present population of humans across the world and then tracing back them to earlier times by matching these genomes with each other. As the genome consists of a very long sequence of the gene chains it is imperative that such a study can be carried out only by use of sophisticated scientific methods using the computer for data analysis and data assimilation. The book has nicely brought out all the new developments in this area and how that data is useful in finding the movement of ancient people across the globe from one region to another.

About the Book

The book consists of three parts. The contents of each part are reviewed and briefly described as below -

Part I - The Deep History of Our Species

This part explains how the sequences in the genome explain who we are and how it is linked to our all ancestors back in time. A human biological cell has two genomes one from father side and one from the mother side. Each genome has 23 chromosomes in which DNA codes are stretched. Now during reproduction the chromosomes come from father as well as mother and splicing between the two takes place and the resulting chromosomes carry the pattern of all earlier generations in it. The DNA codes were accordingly transmitted from one generation to another. So analysing the genome will give insight into the earlier species and ancestors of that particular human being. The study of DNA sequence in the ancient bone samples found in archaeological excavation gave a stunning result that the Denisovans and Neanderthals coexisted with the first humans and as per archaeological studies there were some cognitive skills in those two extinct species which were later fully developed in the first humans. This was a great finding and indicated that the two extinct species interbred with the humans.

Part II - How We Got to Where We Are Today

Based on the ancient samples, the spreading and extinctions of species were inferred and migratory movements were indicated. The samples from Europe, America, Near East, Far East, Africa and Indian Peninsula were analysed and many interesting inferences were made regarding the mixing of cultures in these regions. Some of these scientific facts are not matching with the old history due to obvious reasons and historians have no comments to make on that.

Part III - The Disruptive Genome

This is the last part and in it, the author has discussed in details the genomics of race and identity and how genome studies can help in the commercial exploitation of these methods as tools in the hands of specialised service providers for genetic typing and ancestry determination. In the last chapter of this part the future scope of genome studies and ancient DNA typing is presented by the author as a future perspective.

About the Author

David Reich is a geneticist and professor in the department of genetics at Harvard Medical School. He joined Harvard Medical School in 2003. He is also an associate of the Broad Institute. His research studies are in the field of comparing and analysing the human genome with those of chimpanzees, Neanderthals (one of the extinct later species in the human evolution) and Denisovans (an extinct species or subspecies of archaic humans). He is a pioneer in the field of analysing the ancient human DNA for deciphering the past. He is a recipient of many awards including the 2017 Dan David prize in the Archaeological and Natural Sciences for the computational discovery of intermixing between Neanderthals and modern humans.

He was named in 2015 as '10 people who matter' by the Nature magazine. He was awarded this honour for his contribution in transforming ancient DNA data from niche pursuit to industrial process.

Conclusion

For those who have an interest in the evolution of human species and their migration across the globe during a large geological period, this book is a treasure house assimilating all the information on genealogy and distribution of type of human species in past. This is also a rich source of how the ancient genome is found out from old bone samples of earlier species and prediction of their habitat at that time. This book is equally good for biologists, anthropologists, geneticist and archaeologists. The book is written in a simple explanatory style and even a common reader can derive a lot of knowledge in this specialised field after reading it.


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