Q&A with Developmental Biologist Scott Gilbert

Scott Gilbert

Heard the one about the philosopher, the theologian, and the scientist walking into a bar?

“Really, it happened,” says Scott Gilbert, Howard A. Schneiderman Professor Emeritus of Biology. “Then we went upstairs to a meeting of an ecumenical panel, and the moderator asked each of us: ‘What’s the most important story that needs to be told?’ The philosopher talked about The Enlightenment. The theologian said it’s salvation through god’s grace. Then I replied that the embryo, the creation of the body from the fertilized egg, is the most amazing story ever.”

Propelled by a zeal for scientific discovery, Gilbert continues to add chapters to that story. Whether it’s introducing the study of ecological evolutionary developmental biology in Nature Review Genetics or rebutting claims that there is scientific consensus on when life begins for The Huffington Post and Wired, Gilbert delights in the discovery and dissemination of developmental biology.

Foremost on Gilbert’s mind, though, on a recent Friday afternoon in his office is the second edition of Ecological Developmental Biology, which he recently co-authored. It contains some “game changers,” he says, for the way we think about subjects such as evolution and childbirth. Below, Gilbert discusses the key discoveries of the book as well as his disappointment with how science is being discussed ­— and misconstrued — in politics.

What is a key takeaway from the new book?

We’re finding that the environment — things like temperature, diet, the presence of competitors, and the presence of predators — influences how animals develop. And that animals have actually evolved the ability to respond to the environment while they’re developing, so that, of all the potential phenotypes, the potential manifestations, that it could generate, the one that actually forms is that which will be most fit for the environment. The environment is still selective, but it is also instructive. There’s an active relationship between the developing organism and its environment. That’s really a game changer. 

Can you give an example?

There’s a butterfly from Malawi that has these beautiful eyespots, and the eyespots deflect predators as it flies. It turns out that the high temperatures are inducing the genes that make the eyespots. In colder weather, it’s not a flyer; it’s a walker. And it looks like a leaf. The cold weather prevents the eyespots from forming, and the butterfly looks like leaf litter. So, depending on temperature, these butterflies develop differently, and they develop with coloration that allows them survive in the season they develop in.

In most turtles, sex is also determined by temperature. This whole aspect of development was not being discussed in the scientific community until very recently. It was all about the genome and how genes programmed development. And so what Ecological Developmental Biology is saying is that, actually, part of the program is to allow the environment some informative roles, and that’s why these animals survive.  

Were there other findings that surprised you?

Another thing we say in the book, probably even more radical, is that we don’t develop from a single genome. It usually has been thought that you’re a fertilized egg, and all the cells in your body are the product of the fertilized egg. Now, we find that more than half of the cells of the body are bacteria. And these bacteria are not merely fellow travelers using our food or making some vitamins. These bacteria are necessary to complete our development. This is a whole new area of biology. It basically says that we’ve subcontracted to the bacteria some of our developmental signals. That means mammals don’t make their gut immune systems or their gut capillaries, which are really important, without the presence of certain bacteria. This is a significant shift in our thinking. Bacteria are not our enemies — most of them actually our friends and are essential to our normal development.

What are the ramifications of these findings?

What we’ve thought of as selection of individuals is actually the selection of a team. Which makes perfect sense. Football fans know you might have the best quarterback in the world, but if he doesn’t get pass protection, he’s nothing. It’s the team that goes on, not the individual. This makes a lot of sense in biology as well. In addition to the competitive notion that we have of evolution, the battle of all against all, we also have a cooperative notion, too. So that’s a new thought that’s being put onto the evolutionary theory platform. It also has a lot to say about health, which really has not been said before. I think it’s kind of the new frontier of biology. This means that there are important new questions to study, and people like Swarthmore’s Liz Vallen are entering these new areas.

What sparked your rebuttals to claims of there being scientific consensus on when life begins?

I was actually invited to speak about this at the Vatican; I believe I was the diversity promised in their grant proposal. The Republican presidential candidates in particular say that all scientists agree that life begins at fertilization. I was really angry when Governor Huckabee said this on The Daily Show and Jon Stewart did not contradict him. This is the view that DNA is your essence and you get your unique DNA when the sperm genome meets the egg genome at fertilization.

But there’s another point of view many embryologists have. This is that individual human life begins about at least 12-14 days later, when the product of the fertilized egg can no longer form twins or triplets. This is the time of gastrulation, when cells are told what they’re going to become and the embryo can only become one baby. Another group of scientists says that since the loss of the EEG pattern, or flat lining, is death, shouldn’t, by that standard, the acquisition of the EEG pattern mark when you’re a person? And that’s weeks 24-28, right around the same time as viability. And of course you have another view that maintains life begins at birth. And there’s a whole other group of scientists, maybe the majority, who consider this a silly question, certainly not a scientific question. They feel there’s no point at which we can say, it’s here and not there. So the only thing that we can say with absolute certainty is that there’s no consensus.