Who We Are and How We Got Here Book Summary - Who We Are and How We Got Here Book explained in key points

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Who We Are and How We Got Here summary

Name: Who We Are and How We Got Here
Rating: 4.4 (142 reviews)
Author: David Reich

David Reich

Ancient DNA and the New Science of the Human Past

4.4 (142 ratings)

28 mins

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General Knowledge Culture

Table of Contents

Who We Are and How We Got Here
Summary of 9 key ideas

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What’s in it for me? See how our entire species’ history and future is encoded in our genome.

Human civilization stands at a crossroads. The world has never seemed smaller nor more connected. But not everyone is happy. Some politicians complain that we are under threat from other cultures different to our own, while a few call for the embrace of difference, proclaiming that equality is the way forward.

These may seem like modern issues, but, as these blinks show, to understand who we are and where we’re going, it’s important to understand our past.

DNA, genetics and the understanding of science can help us know our place in the world and how we should relate to people around us. As these blinks show, the history of our species is one of constant change and migrations. Ours is truly an intertwined and intermingled ancestry.

In this pack, you’ll learn

how we know Madagascar is linked to Taiwan in human history;
why ghost populations aren’t something that should be giving you the spooks; and
just how closely you might be related to Neanderthals.

Scientific advances in genetics give us unique insights into early human history and development.

DNA analysis is a wonder of modern science. It means scientists can get to the root of understanding who we are and from where our species comes. But it can be tricky to get your head around.

A good metaphor would be a grenade that’s exploded in a room. The effort required to gather the scattered shrapnel and work out an exact picture of where each bit came from is a not dissimilar task to DNA analysis.

But what exactly is DNA? Well, DNA molecules make up the human genome, the genetic code that each of us inherits from our parents. DNA consists of twin chains of molecules called nucleotides made from the chemicals adenine (A), cytosine (C), guanine (G) and thymine (T). Each chain is about three billion chemical blocks in length.

In contrast, genes are fragments of these chains, generally around a thousand nucleotides long. Each gene is an instruction that tells us something about how the body is built.

Random variations in these inherited sequences are called mutations. These occur roughly once every thousand nucleotides. Mutations are what make us individual, and they are also the means by which individual ancestry can be determined. If you compare two people’s mutations, the more differences you find between their genes, the further they are away from sharing a common ancestor.

One big impact of DNA study is that it has changed our views on evolution.

Scientists used to think that subsets of the human species evolved in parallel to each other on different continents. For instance, that European humans evolved in Europe or Indian humans evolved in India.

However mitochondrial DNA, which is inherited through the maternal line, has revised scientists’ opinions. All humans today are descended from a single female ancestor. She is known as “Mitochondrial Eve,” and she lived in Africa no more than 200,000 years ago.

If the old multi-regional theory held true, then any shared ancestor we had would be close to an incredible two million years old and part of the dispersal of Homo erectus globally around 1.8 million years ago.

However, when Mitochondrial Eve is seen as our shared ancestor, then modern humans must have evolved in Africa and only spread across the world 50,000 years ago.

The ancestors of modern non-African humans interbred with both Neanderthals and Denisovans.

So, 50,000 years ago, the ancestors of modern non-African humans started to migrate out of their original continent. On their journeys, they encountered other species of humans descended from Homo erectus, including Neanderthals. But, within 10,000 years, they had proved so dominant that they were the only human species left.

Neanderthals are an interesting bunch. As a species, they were physically quite distinct from modern humans due to their large frames and projecting brows. Those features partly explain why they have a reputation for being “primitive.” But archeological finds demonstrate they were just as sharp as modern humans’ ancestors.

Migration patterns thousands of years ago informed the ancestry and languages of modern Europeans.

If you compare people from Europe, the Near East and parts of Central Asia, you’ll see that genetically speaking they have an extraordinary amount in common. But look at DNA from between 10,000 and 4,000 years ago, and it’s possible to deduce that there were at least four major populations throughout this area. And each one of these was as distant from each other as modern Europeans and East Asians.

This begs the question: what happened?

Indian ancestry is dual in nature, which is still reflected in its languages and caste system.

The Rig Veda, a foundational Hindu text that’s about 3,000 to 4,000 years old, relates how the warrior god Indra destroyed his enemies’ fortresses and established a new land for his chosen people, the Arya. Fortress remains in the Indus Valley in northern India can be dated to this period. So does this mean there is some truth to the legend?

Today, there are two main branches of languages in India, Indo-Aryan in the north and Dravidian in the south. A 2007 DNA study showed that all Indians are a mix of two ancient populations, one called Ancestral North Indians (ANI), who were related to Western Eurasians, and the other Ancestral South Indians (ASI), who aren't related to any populations outside of India.

Native Americans are descended from two separate migrations, but their exact history is not yet clear.

Looking at genetics also gives us some idea about where Native Americans originated from.

In 2012, the author conducted a study that determined that all Native Americans from Central America southward were descended from a single population, which he named the “First Americans.” Supposedly they migrated to America sometime after 15,000 years ago.

Modern East Asians are descended from migrations that began in the Chinese agricultural heartland.

Humans have made East Asia – China, Japan and Southeast Asia – their home for at least 1.7 million years. We know that because that’s the age of the oldest Homo erectus skeleton found in China. As the country still holds one-third of the world’s population today, we can be sure that an awful lot of migration has occurred in the intervening years.

The author’s laboratory has conducted studies which show that there are three main East Asian populations, descending from two ancient lines: the Yangtze River Ghost Population and the Yellow River Ghost Population.

Africa has seen just as much population movement as the rest of the world.

Sometimes, people make the mistake of presuming that the migration that took modern non-Africans out of Africa 50,000 years ago was the last population movement that happened on the continent.

But this is far from the truth. There have been four major expansive migrations in Africa in just the last few thousand years.

Population mixing is sometimes driven by gender inequality among social groups.

The 1973 sci-fi novel Race Against Time is based on an interesting conjecture. It suggests that by the year 2300, humans would have turned into one “standard” population, losing biological diversity in the process.

There’s a problem with the premise, however. It’s built on the idea that population mixing that took place over the last few centuries is unique in human history. Genome analysis shows the truth of the matter: diverse populations have always bred with each other, simply as a result of frequent population movements. In practice, that sometimes meant couplings of powerful men with women from less powerful populations.

DNA demonstrates that differences exist between populations, but they don’t justify racist generalizations.

Back in 2006, the author was studying the genomes of African-American men. He was trying to work out why prostate cancer occurs 1.7 times more often among that group that among Americans of European ancestry.

His lab identified one part of the genome which contained at least seven factors that raised the risk of prostate cancer.

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What is Who We Are and How We Got Here about?

Who We Are and How We Got Here (2018) takes readers on a journey through the world’s anthropological history, demonstrating that people have continually migrated and mixed over time. Recent scientific advances are allowing scientists to study human DNA from the distant past and compare it to that of those alive today. The insights about humans’ origins are both fascinating and revealing.

Best quote from Who We Are and How We Got Here

Neanderthals were first discovered in the Neander Valley in Germany – tal being German for valley.

—David Reich

Who should read Who We Are and How We Got Here?

Scientists with burgeoning interests in anthropology and languages
Ethno-nationalists looking to have their views challenged
Genealogists looking for the bigger picture

About the Author

David Reich is a professor of genetics at Harvard University and a leading expert on ancient DNA. He was commended in 2015 for his role in the ancient DNA revolution and received the Dan David Prize for Archaeological and Natural Sciences in 2017 thanks to his work uncovering the interbreeding between Neanderthals and the ancestors of modern humans.

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