Sign In

Remember Me

Bruce Lahn Interview

Dr. Bruce Lahn is the William B. Graham Professor of Human Genetics at the University of Chicago. As a student at the University of Beijing, he helped organize some of the first pro-democracy protests in the Chinese capital. By the time these protests evolved into the mass demonstration at Tiananmen Square in 1989, Lahn had moved to Harvard. Later, Dr. Lahn earned a PhD from MIT.

In addition to his scholarly titles, Dr Lahn is the founder and Scientific Director of the Center for Stem Cell Biology and Tissue Engineering at Sun Yat-sen University in Guangzhou, China. The breadth of his work in two cultures also includes neurogenetics and mammalian biology.

C.E. Atkins: Can we begin with some background on your work on the evolution of the human brain and your finding that it’s still evolving?

Bruce Lahn: Yes. We started out looking at genes that might be important for human brain evolution by comparing specific genes in the human genome with sequences in other species, particularly other primates. The goal was to understand genes whose changes have been important in the emergence of the human phenotype, especially the enlargement of the human brain and all the great things that came along with that. We were not actually looking at evolution within the human species. We published a paper showing that genes important for brain development seem to have evolved more rapidly in the evolutionary lineage leading to humans when compared to nonhuman primate lineages or non-primate mammal lineages. This indicated that there has been an acceleration in the pace of evolution in genes that regulate brain development in the origin of our species.

You can envision the evolutionary tree where one branch goes to the human species while many other branches split with the human branch, either long ago or more recently, and lead to other species. If you draw a line in the lineage leading to humans, that’s the lineage where the most dramatic changes in brain size and structure have taken place. We zeroed in on several specific genes that might be particularly relevant to human brain evolution. We think that they are particularly relevant because the accelerated evolution of these genes has been dramatic.

In addition, we found evidence that the accelerated evolution seen in these genes is really due to positive selection rather than chance. That is, selective forces have driven these peculiar changes. It’s almost like the intelligent design argument. If something looks too unusual, it’s unlikely that it’s random; there’s a purpose to it. We think that natural selection has driven these changes to accomplish certain functional ends, that is, selection for an altered biological function of these genes.

CE: So the mutation process continues.

BL: Yes. What happens is a random-chance mutation that is advantageous strikes only one individual in a population belonging to a particular species. The person who has that mutation will reproduce a little better. Some of their kids would inherit this mutation and also reproduce a little better because the mutation makes them more attractive, stronger, whatever. Over time, this mutation would spread in the population to the point where it basically takes over the entire population and everybody has it. So we saw, based on comparisons between humans and other species, that signatures of adaptive evolution for these genes meant that they have gone through many of these sweeps. One sweep fixing one advantageous mutation, another sweep comes along and fixes another.

CE: Could have even been the same gene?

BL: Could have been the same gene, but not necessarily the same base, that is, different sides of the same gene. Just like you can tweak many parts of a car to alter its performance, make the shape more aerodynamic, the engine stronger, there are many ways to tweak a gene toward a certain functional end. It doesn’t have to be just one specific letter in the spelling of that gene. So different parts of the gene were struck at different time points in evolution by mutations and because they were advantageous, they swept the entire population. And that happened many, many times.

And when we compare the end product of a long evolutionary process with many such sweeps, comparing Homo sapiens with other species, we see that Homo sapiens actually accumulated many, many changes that don’t appear random. So we asked, given that the observed differences between humans and other species are likely due to the repeated occurrence of these sweeps, is it possible that we could observe one of these sweeps in action now?

In other words, in the recent past has a new mutation landed on one individual to make that person a little more fit? We ended up examining the variation of two of these genes and found that there indeed has been an advantageous variant in each of these two genes that arose very recently. One mutation appeared roughly 6,000 years ago and is now found in over 30% of all the chromosomes in the world. And another gene we looked at, that first mutated about 40,000 years ago, is now in over 70% of the chromosomes out there. It’s almost like the cell phone. The first person has it and everybody wants it.

CE: And these genes currently spreading through the population are involved with brain development?

BL: Yes, we think the evolution of these genes, be it in the course of the emergence of the human species or in the more recent past, likely has to do with brain biology because these are key brain genes. Their functions have to do with how the brain develops and how it operates. The question is, what does the new variant in these genes do? What is the novel function that has been selected? Does it make people more cunning, more coordinated? We don’t know, but we are doing association studies.

We look at people who have one of the three genotypes, people with both new chromosomes, people with one new and one old, and people with both of the older variant. Then we ask: Do people with these different genotypes on average have a different manifestation in some aspect of brain biology? The usual suspect is carpentry abilities, which is what we focused on. That’s a study that is on going right now. There’s some hint that that could be the purpose.

CE: So cultural evolution not only has a genetic base, it may even be somewhat specific. Can you speak to the relationship between cultural evolution and genetic evolution?

BL: Okay, let me make a general statement that has to be true and then make an extension of that statement that is likely to be true. The statement that has to be true is: The fact that humans are capable of advanced culture and other species are not must be genetically based. Humans are cultural not just because of the environment, but rather because humans have acquired a set of genetic changes that other species didn’t have the great fortune to acquire. Cultural evolution definitely has a genetic basis. Nobody would deny that.

The extension of that statement – that more recent cultural events might have a genetic basis as well – has to be considered more cautiously. The emergence of art, language, complex tool-making and tool use, settled cities, complex social hierarchies, these might have a genetic component but not necessarily. I would argue that if the dramatic differences between humans and more primitive species, or our ancestors from way back, if those differences are due to genes – which no one will argue – then the smaller increments must also sometimes be due to genes.

It’s not as if we were devoid of culture and then suddenly acquired all the necessary mutations to develop culture. It has to be that there is selection along the way incrementally for culture. So we become a little smarter. It doesn’t mean that we could suddenly acquire language, but we could make our lithic tools a little more complex or something. Going back 5 to 20 million years, there must be small genetic steps that accompany small cultural steps.

It’s not outrageous to say that more recent cultural events might also have a genetic component, though, conversely, they may be purely cultural. I would argue that even though in the long run cultural capabilities have a genetic basis, it doesn’t mean that each cultural event has a genetic correlate. Maybe several cultural events have one or several genetic correlates that didn’t all occur at the same time. It isn’t that the emergence of written language necessarily had a genetic correlate, but I think it’s a reasonable hypothesis to explore.

CE: Okay, expanding on this interplay between biological and cultural evolution, we have a biological environment, a cultural environment and now it seems we have a technological environment. Do you think that cultural evolution feeds back on genetic/biological evolution? For example, could we eventually see selection for technological intelligence as well?

BL: Genetics, changes in DNA can contribute and can trigger cognitive/cultural evolutionary events. The converse could be true, too, in that once you have achieved certain cultural and cognitive states, originally due to genetic changes, then these states may also turn around and enhance the selection of genes. In other words, as humans become more complex, more capable of implementing social, technological and cultural environments that are more selective toward greater and greater cognitive complexity, selection for further genetic changes for tool use or producing even smarter individuals becomes even more intense than when human cognitive abilities were more primitive. It may be that this partly explains why human cognitive abilities and structure just took off. Maybe it was just chugging along – humans, apes, everyone just chugging along – and suddenly, by chance, it reached a certain threshold, some critical point where beyond that it just blows up.

I’m not the first person to say this. A lot of evolutionary psychologists have speculated about this. It remains speculation at this point, but I think it’s pretty reasonable speculation. So I think there is this interplay between genetic and cultural evolution.

CE: Would cultural selection become structured biologically?

BL: I think it would.

CE: Do you think the rate of evolution is increasing?

BL: I think so.

CE: Why do you think the rate of evolution is increasing? Is it a network that is more integrated, with more feedback loops driving the system?

BL: I don’t know. If you look back at the history of life, you see these events where a species has stayed true to its original form for a very long time and then suddenly morphed into a different species. The original form may still persist to the present day or may have perished. Stephen Gould coined the term punctuated equilibrium to describe the fact that evolution seems to have these long periods of stasis that are punctuated by sudden morphological leaps. I think that the fact recent human evolution seems to be one of these leaps may be due to a similar set of reasons. Punctuated equilibrium is a phenomenon that is observed quite frequently throughout the tree of life. For example, the emergence of mammals and birds occurred pretty rapidly.

Luckily, there are a lot of fossils of recent human evolutionary development and we can reconstruct every key step, such as bipedalism and the enlargement of the brain. All the major anatomical features have intermediates that were recorded in the fossil records. I don’t know if you read that the first fossilized chimpanzee was just found. It was one tooth or a couple of teeth.

Early hominids lived on the open savannah. The early hominids were fossilized and the chimps were not. Imagine if the situation was reversed. Creationists would have a field day. There’s no missing link. They still claim there’s a missing link. I can go to a museum and line up the skulls with all the intermediate steps that go from a chimp-like species to a human-like species and they would still say there’s a missing link.

CE: They have to say something I guess. Okay, the late British mathematician, Sir Arthur Eddington, said: “The stuff of the world is mind-stuff.” Robert Wright, in his book, “Nonzero – The Logic of Human Destiny,” makes a strong case that both biological and cultural evolution have a direction. Then there’s the English biologist, Rupert Sheldrake, with his morphic resonance and morphic fields concept, information fields that contribute to the evolutionary process. So I read about and see these evolutionary patterns for greater and greater integration, greater complexity for greater information processing ability and processing speed. To me, reality seems to be simultaneously noun and verb, both information and an increasingly integrated information processing network. I kind of see natural selection as a vast, networked, information processor unit.

BL: (Laughs) Yes, yes. This is all obviously going to the speculative and metaphysical domains. I can probably speculate as well or as badly as anyone. I’ve been thinking about this and I’m sure most inquisitive people have for many years, obviously without (a) good answer. My sense is that we understand a very limited aspect of the life phenomenon because our perspective is such that we cannot see the big picture.

One time I was flying through the clouds in an airplane. All I could see was randomness, patches of mist flying past the window. The plane would rise above the clouds and suddenly, I could see large patterns of clouds. So I think there are governing principles, not just of life but of the universe that are at levels not necessarily bigger in scale, but maybe in a different dimension, that are not readily observable by us.

Why does it have to get more and more complex? Why does it have to acquire self-awareness? The fact that these things happen may have to do with some guiding principle that we cannot observe or readily deduce. What is it that’s driving life forward in addition to the Darwinian process? Darwinism is very understandable on a smaller scale, but I think that there is something about the life phenomenon that the Darwinian theory doesn’t fully explain, at least in a way that is satisfactory.

CE: And with new ideas that speak to a more encompassing explanation, it wouldn’t be that Darwin was wrong. We would just be adding to his base.

BL: Exactly. For example, Newton’s theory was dramatically expanded upon by later people. In this case, 30, 40, 50 years from now, someone might come out with a more encompassing set of theories and you incorporate the Darwinian principles only as some sort of basic building blocks in a much more complex theoretical edifice.

The Darwinian theory says that if you give me many, many complex systems representing different species, over time they will change. But not only is the pattern complexity evolving, the level of complexity is also increasing over time. The Darwinian theory does not predict that, doesn’t necessarily say that the degree of complexity should increase overall for the entire system or set of systems. And that really is fascinating. We probably started from some sort of single molecule life and then it becomes multi-molecular with a membrane. It’s still a single cell, but then becomes multicellular with each cell doing different things. Now we seem to be evolving into a sort of society where each individual is performing different roles, almost society as a life form.

CE: As if individuals in society are like the individual cells in the brain.

BL: Ants, and social insects, each one almost behaves like a cell.

CE: It makes me think of the increasing specialization in the economic structure. All right, shifting gears here, is the brain the fastest evolving organ in the history of evolution?

BL: In terms of complexity, I think so. Not in size, the horn has evolved to a very large size very quickly. But it also doesn’t take too many genes to make a horn bigger. So in terms of complexity, I would be hard-pressed to come up with another organ that has acquired complexity at the rate the brain has.

CE: Getting back to information processing, on a more personal level, have you found that when you are conducting an experiment or in your search for information, that the information you need comes to you? You find the right book, the right paper. Have you noticed this, a pattern of information coming to you?

BL: I can tell you that I’ve had a lot of hunches that turned out to be good and in retrospect it was almost too serendipitous to be true. I would suddenly hear certain information in another context that would make a big difference in my research direction. It’s almost as though there’s a purpose or someone is whispering to you. I think that this phenomenon may just be that when one is so immersed in something, so versed in a particular field, that productive thoughts come to that person in a way that that person doesn’t even know how or why those thoughts emerge.

Very simple example, I’ve noticed a lot of people in my lab have said that when they do an experiment the first time, they don’t quite know how to do it and they follow the protocol exactly and it will fail. The second or third time they repeat it, then it works. And they didn’t do anything different. And after that it works every time. Surprisingly, if this thing works every time and it only failed 2 out of 20 times, how come those 2 times are almost always the first 2 times?

I think that something has been learned. When you come to understand the system better, that allows you to make judgments in ways that are perhaps subconscious, that are more likely to be correct. I think in terms of information gathering, when you are versed in a particular subject, there’s a selectivity that becomes more and more robust and more likely to be correct that is below consciousness.

CE: On another topic, I’m curious about the evolution of a new human species. Jonas Salk wrote in his work “Anatomy of Reality,” that, because as a species we are so destructive right now, that some people are going to withdraw from the culture. They will be able to survive on the fringe of the culture as cultural mutations. He called this collection of outposts “sociometabiological islands of sanity.”

BL: (Laughs) I love it.

CE: (laughs) It is great. Anyway, the mind, in sociometabiological evolution, would drive biological or genetic evolution. And while Salk doesn’t address the specific mechanisms of speciation, it seems that changes in culture and behavior, directed by the mind, would feed back and show up genetically, driving the origin of a new human species.

Conversely, the late eminent biologist Ernst Mayr, in his book “What Evolution Is” wrote: “What is the probability that the human species will break up into several species? The answer is clear: none at all.” I think he felt that there were no isolated pockets of humans where speciation could happen.

But Salk’s idea is that the mind, through its selection, would create these sociometabiological pockets. And while these “fringe” human beings would retain the biological capacity to create offspring with people of an older variant of philosophic and cultural selection, they would choose not to, and over time generate a new human species.

BL: I think it’s a reasonable scenario. There are a lot of species that could breed in zoos, but in the wild they are not willing to breed, therefore they are a different species. My sense is humans are almost certainly going to speciate, that we are going to become a very different species, one that appears and behaves very differently from humans today. I have no doubt, not even a trace of doubt that this is going to happen. This is not even a hypothesis. It’s almost as if you are asking me if humans are still evolving. Of course. If humans have come such a long way, you can’t tell me that the Darwinian process would suddenly stop. Similarly, speciation is a process that is so inherent to the life phenomenon that it really has to continue.

Now, how is it that it occurs? I don’t know. I can give you a couple of scenarios. And I agree with the one you just brought up. I think that is a very reasonable one. Another one is, you’re talking about cultural evolution, technological evolution feeding back on genetic evolution. I can certainly imagine a situation where feedback is actually deliberating information on our genetic code. Some people figure out a way to change their genome to survive better. That literally changes the whole game of evolution. You can imagine that would create a situation where a substrata of people, people with the ability to access resources who are also cognitively receptive to this idea, would suddenly be able to evolve at a high rate.

Lee Silver wrote a book about this, that genetically engineered humans may trigger speciation. So you can imagine that as more genetic engineering is done on our genome, there will be incompatibility that is created by these changes introduced into the genome. It could be one gene.

CE: One gene?

BL: Yes. In the wild, people have found that one gene has contributed to speciation. The species who have that gene and the ones who don’t cannot breed with each other. There’s a lot of work done with flies; one gene can be key to speciation.

CE: So that can be the isolating mechanism?

BL: There doesn’t even have to be biological incompatibility. If you have that gene you are just inordinately attracted to people who have that gene and not attracted to people who don’t. It could be due to an olfactory response or it could be cognitive. Who knows what?

CE: Why would Mayr and others see no human speciation?

BL: I think there are a number of intellectuals out there full of good intentions who like to believe that in addition to living up to Darwinian principles, they also want to live up to some Judeo-Christian concept of what a human should be and what the human species should be.

The idea of speciation just flies in the face of that ideal, especially in the context of racism (and) genocide. The idea of speciation also implies that maybe some are better. Discrimination and post- biological difference may even imply conflict where one species or sub-species annihilates the other, which has been attempted in the past. That conflicts with their ideals, so intellectuals try to find every reason to reject that hypothesis.

I also think they are too focused on how humans behave today. There is no gene flow that would maintain all the different people as one species. There may be key genetic or cultural events that would drive isolation, as you said, where people group together and speciation starts there. It may be other selective pressures that drive speciation. Nevertheless, we can all anticipate that once it is experienced, it will make perfect sense.

CE: Staying with human speciation, Erwin Schrodinger speculated that humans may be transitioning to a new type of human, what he called an “animal social,” which is a bit like the superorganism concept found in some social insect species that we talked about earlier.

And Theodore Sturgeon, in his sci-fi novel “More Than Human,” talks about a new human species he calls Homo gestalt. It’s a grouphuman species, people who function as an integrated whole by way of highly developed intuitive/psychic abilities.

I just feel like selection for intuition makes sense because it fits with the pattern for increased processing speed. For example, if instead of the nuclear family, some people become the molecular family, a self-organized structure where survival is more integrated, driving selection for faster inter-human information processing/sharing. Do you think there could be selection pressure for increased intuitive ability?

BL: Absolutely. I think there has to be selection for so-called intuition in a way that is devoid of rational reasoning. You know you can feel something, but you don’t quite know why. In fact, I think there is a very powerful level of intelligence that is undertapped. I think science tries to break down things into understandable components or build complex systems up from individual blocks. It’s a very powerful approach.

But I think the real world is so complex that that approach alone is not sufficient. And that is where you need intuition. Where somehow natural selection figures out a way to synthesize information that does not need your reasoning. We don’t know how that works.

Just like when I was riding in the plane, I could see patterns of clouds that were very striking that I wasn’t able to deduce by watching molecules bouncing together. I didn’t need to go through complex computations to appreciate it. That is the pattern that will emerge. I think as we acquire more cognitive abilities in the domain of reasoning, which has been very powerful, we are also going to acquire intuitive abilities in domains where reasoning and cognitive abilities will never get us there.

CE: That’s great, very exciting. Okay, to close, I gotta ask you, being immersed in genetics and the whole Darwinian perspective, does it make you a ruthless S.O.B.?

BL: I ask that question to myself all the time. It’s a very profound, important question. I ask myself that question because from a Darwinian point of view, to understand how the system works, I have to step away and look at it dispassionately. I cannot look at it from a right and wrong, moral perspective. At the end of the day it’s competition for survival, for resources. And if a brutal human phenomenon such as genocide can be explained in the context of that, so be it. That’s how it is. Does that make me no longer sensitive to all these important values, the values of equality and compassion? I think it doesn’t. Politically, I’ve always been a “progressive” and I remain so even after being immersed in evolution for a number of years.

I see it this way. Philosophers wonder if once people reach a certain state of mind where they totally understand where they are and know for sure that there is no higher being and that everything is guided by physical principle, will they decide that being alive means being enslaved to some outside process and ask why should they even stay alive? What’s the point of loving your parents if they’re just another bag of atoms? I think that on one hand we can see ourselves as a bag of atoms that do certain things that atoms do.

On the other hand we can still follow our human instinct. I still love my parents and I still have compassion for downtrodden people. I still make donations to causes even though they may or may not tie into a particular Darwinian principle that I happen to believe in at the same time. I don’t believe that because I have compassion for other people, that my passion for the Darwinian theory stops either. I’m trapped in my body and I have certain desires, aversions and certain needs. Just because I recognize these as practical and physical aspects of life doesn’t mean that my life is devoid of the personal aspect.

If I’m on a plane that is going down and there is no way out, it doesn’t mean that I can just drop my fear, enjoy the last minute of my life and finish my orange juice. The brain has an emotional center and it has a rational center. Pursuing science, at least the execution part, has to do with the rational center, but what I do, which includes pursuing science, and what I like and don’t like comes from the emotional center. We don’t know how that works, but it doesn’t mean that it ceases to have an important function.

CE: Okay, Dr. Lahn, thank you so much. Absolutely fascinating stuff.

BL: Sure, I enjoyed it.