In modern times, our lives have changed tremendously by gaining control over nature. The advent of vaccines, antibiotics, antivirals, and better sanitation has dramatically reduced our physiological challenges. In the present day, we enjoy a much more secure food supply than we did a hundred years ago.

We live at a time where cultural evolution can be very, very, very rapid, but our biological evolution seems relatively stunted. Why is this? Why is everything about our civilization changing constantly, except our bodies? 

Biologist and author Sean B. Carroll unveils why biology isn’t evolving as rapidly as culture.

SEAN B. CARROLL: Human life has changed so much in modern times. If someone could parachute in from say, you know, 1800 to the modern day, it would be a bewildering experience in so many facets. Whether it's how we make our food, transportation, energy, disease, medicine, enormous transformation of how we live. And our lives have changed a lot by really gaining control over nature. If you consider nature, vulnerability to the elements, which includes things like drought and famine, which are gonna affect the abundance of food and water, infectious disease, wild animals, etc., almost all that has changed for most people on the planet. And so that's really changed, fundamentally, the quality and quantity of life. And central to a lot of these changes are, for example, the science of biology: by discovering more and more about how nature works. And that knowledge has been power. For example, we didn't know about viruses and bacteria until the last 150 years, and we didn't know much about how to manage them until probably the last 70 to 75 years. In the 19th century, a very large percentage of Americans had TB. You know, now we would think about that disease as, you know, "Where did that go?" In the 1960s in the United States, there was a rubella outbreak. We don't hear the word rubella much because it's the R in the MMR vaccine. Smallpox, which killed tens and tens and tens of millions of people, not only has been controlled, it has been eradicated from the planet. From every nook and cranny of the planet, smallpox is gone. So the advent of vaccines, of antibiotics, of antivirals, and of better sanitation, has dramatically reduced what people deal with. And with respect to agriculture and food production, a remarkable statistic is that around 1900, perhaps 40% of the United States labor force was involved in farming and agriculture in some way- that's now 2%. And that 2% is providing a lot more food for a lot more people than it ever did. And of course, exporting around the world. So the efficiency of agriculture, the productivity of agriculture is remarkably different. Some of that is due to automation, but a lot of that is due to discoveries about better seeds, better ways of nourishing crops, better ways to fight off plant diseases. You know, now we enjoy a much more secure food supply than we did a hundred years ago. So these are important biological impacts on us, but I often get the question, you know, And that, I don't have a really clear picture of that. If you go back in time, say 60,000 years ago, when humanity left Africa, when the first migration of Homo sapiens out of Africa happened, and this was gonna lead to the settling, you know, of humans on five more continents. If we had sort of stayed as isolated populations, unconnected, not able to travel the seas, not able to go across land, bridges and things like this, then you would have essentially these sophisticated, you know, human populations in different places, but not sharing genes, not sharing culture. That sets up the situation for evolution. I mean, isolation is sort of, you know, evolution's laboratory. This is why the Galapagos finches are such an example of evolution is that isolation factor gives the opportunity for speciation to occur. But because now we are so connected as a species, sharing genes and culture across the globe, that's going to work against sort of whatever biological evolution might be underway because of how we've changed our food supply and changed our relationship to infectious diseases and things like that. And of course, you can see in certain human populations that are specialized to high altitude or certainly across different latitudes in terms of how much sunlight they get. You know, obviously Northern Europeans and Equatorial Africans, we all look differently because those are actually local adaptations. But those aren't fundamentally, you know, speciation events happening. So anatomically and physiologically, I would say, I don't think we've evolved much. You know, cultural evolution can be very, very, very rapid, but our biological evolution is relatively slow. So there's a lot of mismatches, like our physiology, which was wired to seek out various nutrients that might have been very hard to get as a hunter-gatherer, but are now very easy to get at the grocery store, means that, you know, our diets are so radically different than what had evolved, you know, by 10,000 years ago- that's showing up as all sorts of, you know, syndromes in humanity. And perhaps, that's one of the things that overwhelms us is that, you know, biology's not evolving as rapidly as culture.