A Brief History of Everyone Who Ever Lived

1. Human genetics reveals our interconnectedness and shared ancestry

You are of royal descent, because everyone is. You are of Viking descent, because everyone is. You are of Saracen, Roman, Goth, Hun, Jewish descent, because, well you get the idea.

We are all related. Genetic studies show that all humans alive today share common ancestors from just a few thousand years ago. Mathematical models indicate that the most recent common ancestor of everyone on Earth lived around 3,400 years ago.

Ancestry is messy and complex. Family trees are not neat branching structures, but tangled webs. As you go back in time, the number of ancestors increases exponentially until it surpasses the total population. This means our family trees fold in on themselves, with ancestors appearing multiple times.

Geographic ancestry is recent. The genetic differences we associate with geographic ancestry (like European or Asian) only emerged in the last 50,000 years as humans migrated out of Africa. Prior to that, all of humanity's ancestors lived in Africa. So in the big picture, we are all African.

2. DNA is not destiny: Genes interact complexly with environment

For every complicated problem there is a solution that is simple, direct, understandable, and wrong.

Genes are not deterministic. While genes influence traits and disease risk, they rarely act alone or guarantee outcomes. Most human characteristics are shaped by complex interactions between many genes and environmental factors.

The "gene for X" fallacy. Headlines often claim discovery of genes "for" complex traits like intelligence or criminality. This oversimplifies how genes work. In reality:

• Most traits are influenced by many genes, each with small effects
• Gene variants often have multiple, context-dependent effects
• Environmental factors play a huge role in how genes are expressed

Nature via nurture. Rather than nature vs. nurture, genes and environment constantly interact throughout our lives. A more accurate view is "nature via nurture" - our innate tendencies are shaped by our experiences and choices.

3. Race has no biological basis in genetics

There are no essential genetic elements for any particular group of people who might be identified as a 'race'.

Race is a social construct. While there are genetic differences between populations, these do not align with traditional racial categories. There is more genetic variation within races than between them.

Continuous variation. Human genetic variation is mostly continuous across geographic regions, not discrete. There are no clear genetic boundaries between races.

Superficial differences. The visible traits we associate with race (skin color, facial features) are controlled by a tiny fraction of our genes. They don't reflect overall genetic similarity.

Recent divergence. All non-African populations diverged from a common ancestral group just 50,000-80,000 years ago. In evolutionary terms, that's very recent.

4. The Human Genome Project revolutionized our understanding of genetics

Ewan Birney's betting book is a great demonstration of how science works, and the virtues of ignorance.

Fewer genes than expected. The Human Genome Project revealed humans have only about 20,000 genes - far fewer than initially predicted. This highlighted how little we understood about genetics.

Non-coding DNA. Over 98% of the human genome doesn't code for proteins. Much of this "junk DNA" likely has important regulatory functions we're still uncovering.

Common disease, common variant hypothesis disproven. Genome-wide association studies failed to find common gene variants explaining most common diseases. Instead, rare variants and complex gene interactions seem more important.

Missing heritability problem. For many traits we know are highly heritable, we can only identify gene variants explaining a small portion of that heritability. This remains an active area of research.

5. Epigenetics: How environment can influence gene expression

Epigenetics is a fascinating, essential part of biology, still in its infancy, worthy of serious, scrutiny-rich research. It is not magic or new, not heretical, and it won't upend Darwin or gift you supernatural powers over your life and fate.

Gene regulation without DNA changes. Epigenetic mechanisms like DNA methylation can turn genes on or off without changing the underlying DNA sequence. This allows for flexible gene expression in response to environmental cues.

Potential for inheritance. Some epigenetic changes may be inherited across generations, though evidence in humans is limited. Examples include:

• Dutch Hunger Winter effects on grandchildren's health
• Possible transgenerational effects of trauma

Not Lamarckian evolution. While intriguing, current evidence for transgenerational epigenetic inheritance doesn't challenge core evolutionary theory. Effects appear limited and temporary.

6. Ancient DNA is rewriting human evolutionary history

We chip away at the edges of the unknown, a never-ending jigsaw puzzle – science as a way of knowing.

Interbreeding between human species. Ancient DNA revealed that modern humans interbred with Neanderthals and Denisovans. All non-Africans today carry some Neanderthal DNA.

Complex migration patterns. Ancient genomes show human migrations were more complex than previously thought. There were multiple waves of migration into Europe and other regions.

Recent evolution of traits. Many traits we consider typical of certain populations, like light skin in Europeans, evolved quite recently - within the last 10,000 years.

New human species discovered. Ancient DNA led to the discovery of previously unknown human species like the Denisovans.

7. Genetic variation is mostly within, not between, populations

Genetically, two black people are more likely to be more different to each other than a black person and a white person.

85% of variation within groups. Studies consistently show about 85% of human genetic variation occurs within traditionally defined racial or ethnic groups, not between them.

Continuous, not discrete variation. Human genetic variation doesn't cluster neatly into distinct groups. Instead, it varies gradually across geographic regions.

Recent African origin. All non-African populations descend from a small group that left Africa 50,000-80,000 years ago. This created a "bottleneck" that reduced genetic diversity outside Africa.

Superficial visible differences. The traits we associate with race, like skin color, are controlled by a tiny fraction of our genes and don't reflect overall genetic similarity.

8. Genetic determinism in crime and behavior is deeply flawed

DNA is not destiny. The presence of a particular variant of a particular gene may just have the effect of altering the odds of any particular behaviour.

Complex causation of behavior. Criminal or violent behavior results from complex interactions between many genes, environmental factors, and personal choices. No single gene determines such behaviors.

Statistical associations ≠ causation. Studies may find statistical links between gene variants and behaviors, but these are usually weak associations, not causes.

Ethical and legal concerns. Using genetic evidence to explain or excuse criminal behavior is deeply problematic. It could lead to discrimination or fatalistic attitudes.

Ignoring social factors. Genetic explanations for crime often overlook crucial social, economic, and environmental factors that contribute to criminal behavior.

9. Consumer genetic testing has limitations and ethical concerns

Genetics is a probabilistic science, and any action predicated solely on DNA sequence seems to me to be a high-risk endeavour, prone to specious failure.

Limited predictive power. Most consumer genetic tests provide only weak probabilistic information about disease risks or traits. Results are often misinterpreted.

Privacy concerns. Genetic data is highly personal and could be misused if it falls into the wrong hands. Many consumers don't fully understand how their data might be used.

Psychological impacts. Learning about genetic risks can cause anxiety or false reassurance. Results may influence major life decisions in potentially harmful ways.

Oversimplification of ancestry. Ancestry results often oversimplify complex histories and reinforce misleading ideas about race and ethnicity.

10. The future of human evolution is shaped by technology and culture

We have externalized the stomach with the invention of cooking, so we don't have to digest a whole range of chewy molecules, because they are already partly broken down by our unique control of elemental fire.

Reduced natural selection. Modern medicine and technology have greatly reduced many historical selective pressures on humans.

Cultural evolution. Cultural changes now occur much faster than biological evolution. Our ability to pass on knowledge and technology shapes our species more than genetic changes.

Gene-culture coevolution. Our genes and culture continue to influence each other. For example, the spread of dairy farming led to genetic adaptations for lactose tolerance in adults.

Potential for genetic engineering. Technologies like CRISPR raise the possibility of humans directly altering our own genome. This could profoundly shape our evolutionary future.

Human Genetics Adaptation: A Brief History of Everyone Who Ever Lived by Adam Rutherford

1. Human genetics reveals our interconnectedness and shared ancestry
2. DNA is not destiny: Genes interact complexly with environment
3. Race has no biological basis in genetics
4. The Human Genome Project revolutionized our understanding of genetics
5. Epigenetics: How environment can influence gene expression
6. Ancient DNA is rewriting human evolutionary history
7. Genetic variation is mostly within, not between, populations
8. Genetic determinism in crime and behavior is deeply flawed
9. Consumer genetic testing has limitations and ethical concerns
10. The future of human evolution is shaped by technology and culture

Last updated: August 8, 2024