Field of Science

Reddit AMA FAQ

I did a Reddit/r/IAmA AMA yesterday and got a huge amount of questions. Some of them were repeats, so I post them here with answers. I'm planning to do another AMA perhaps next month, so this can serve as a reference.

Update 11/12/13: Randy's interview about this AMA is featured on BEACON's blog.

Q. What came first the chicken or the egg?

A. The egg. All chicken start out as eggs, but eggs evolved long before birds. Lots of animals start life as hard shelled eggs, including of course dinosaurs and reptiles, which birds evolved from. So when the first chicken was born to non-chicken parents (though it is hard to say when that would be, even if we know every chicken ancestor) it came from an egg, just like its parents did. The egg is also the earliest developmental stage, so therefore comes first in that sense as well.

Q. Are you religious?

A. No. I am not religious and I have no faith. I am atheist with respect to any gods that I have heard of. I have been non-religious since I started to think about it as a child. My parents did not raise me with religious beliefs.

Q. Are humans still evolving?

A. We are not done evolving. We still evolve biologically, though there are some aspects of humans life that have been taken over by cultural evolution. Just to mention one prominent aspect: medicine has alleviated many selection pressures. For much of our history a large factor in how we evolved was diseases. Diseases is a very strong selection pressure for evolving resistance. We are now resistant to many diseases that previously killed us, and yet when new ones arise today, we can fight back with medicine. For example, we don't need to succumb to HIV/AIDS, such that only the few that by chance are lucky to be resistant will survive, while everyone else dies (which incidentally is an excellent example of how selection works). As a result in part of medicine (particularly improvements in hygiene), the human population is now as large as it is. However, most people who argue that humans have stopped evolving seem to not have understood 1) that the increase in our population size leads to an increase in genetic diversity, which is the fuel for evolution, and 2) that evolution takes time, and there will come a time (perhaps in hundreds of thousands of years, but I am not so optimistic) when things will change, and the environment will again favor some human subpopulation over others. You can read more about this from my colleague Madhusudan Katti in reply to the sad claim from David Attenborough's that humans are no longer evolving.

Q. What do you think of the Aquatic Ape theory?

A. The aquatic ape theory is not plausible. I do not think humans need to have been semi-aquatic for a while in order to look the way we do (little hair, bipedal, and I forget what else they claim is evidence of it). Tim White once in 2009 told me and Daniel Dennett (who at the time liked the theory) that if it was true, then certain isotopes should be detectable in our bones, which they are not. I don't know the details of this, but can say that it is not a theory that many evolutionary biologists take seriously.

Q. How do you deal with creationists?

A. I start by being as rational as possible, answering their questions and focusing on the biology rather than their religion (which I don't really care about). As long as they try to listen, and acknowledge that I probably know more about it than they do, then we can have a conversation. If and when they start lecturing me, then I quit, as I have no patience for that. I focus on explaining that there is overwhelming empirical evidence for evolution, and give example of what some of it is. I don't have the most patience with people who think one book is all you need to read to learn about the world, though.

Q. Why did you become an evolutionary biologist?

A. I was looking around for a programming job in Santa Barbara, and one professor, Todd Oakley, said that he needed one, but that I should become a graduate student instead. So I accepted. This was extremely lucky, as I had been interested in evolutionary biology for a few years before that. I had even purchased Douglas Futuyma's textbook Evolutionary Biology to read in my spare time.

Q. How much money do you make as a scientist?

A. Not enough. I am a postdoc, which is the job you take after you get your PhD and before you become a professor. Postdocs make between $35 and $55 per year (in the United States), typically between $40k and $50k. Professors make more, up to somewhere between one and two hundred thousand per year.

Q. Have we found the missing link?

A. It's called "transitional fossils", and we have found a plethora of those:

Q. Any advice for an aspiring biologist?

A. Go to college. Read as much as you can muster. Read widely rather than deeply, at least in the first few years. Go to seminars even if you don't think that the talk is about something you are very interested in. You may still learn something, and you may find new interests. And don't be afraid of not understanding everything. No one does, even professors. Discuss everything with your peers. Enjoy it - it's going to be so much fun, intellectually and socially.

Q. Do you find it difficult to get funding for your research?

A. I am a postdoc, so at this stage in my career I don't have to worry too much about applying for funding myself. But yes, generally it is very difficult, as a lot of researchers compete for very little money. The situation is quite bad these years, and applying for grants is the thing I worry the most about for my future. I think the most important contribution from evolutionary biology is simply that it explains our origins, which I think is very important for our curious species. But evolution is also becoming more and more important in medicine and engineering, where evolution explains antibiotic and antiviral resistance , and allow engineers to build better cars, antennae, and other things.

Q. What authors would you recommend for a non-scientist interested in evolutionary biology?

A. Stephen J Gould (mostly his essays from the Natural History magazine, which have been collected in a number of books).

Richard Dawkins (The Selfish Gene, Th Extended Phenotype, Climbing Mount Improbable, and more).
Carl Zimmer (he writes a column for The New York Times, and is the best journalist writing about evolution, in my opinion - and many evolutionary biologists I know would agree. He also wrote a highly acclaimed textbook for undergrads: The Tangled Bank).
Neil Shubin (Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body).
Jerry Coyne (Why Evolution is True).
EO Wilson (Naturalist).
Donald Prothero (Evolution: What the Fossils Say and Why It Matters).

Q. If we found life on another planet similar to earth, do you think the animals would be recognizable? 

A. I think they would be similar to something here on Earth, which has an incredible variety of species.

Q. What is your favorite animal?

A. Cheetah. And corvids, because they are so intelligent and creative (which is largely the same thing). Prehistoric: Argentinosaurus. For evolution: A croatian lizard, Podarcis sicula. Read more about the lizard in this paper: Rapid large-scale evolutionary divergence in morphology and performance associated with exploitation of a different dietary resource.

Q. What is the definition of a species?

A. The most common definition used for sexual species is the Biological Species Concept, coined by Ernst Mayr. It says that two populations are different species if they are reproductively isolated from each other. There are other definitions, but this is the most widely used one when we aren't talking about species that are mostly asexual, such as bacteria, in which case I prefer to use the Ecological Species Concept by Van Valen (1976), which states that a species is a group that occupies a distinct nice (i.e., a unique way of life): "A species is a lineage (or a closely related set of lineages) which occupies an adaptive zone minimally different from that of any other lineage in its range and which evolves separately from all lineages outside its range." The paper is titled Ecological Species, Multispecies, and Oaks. Best title ever.

When house cat and bobcat split from each other, reproductive isolation probably took a while to occur. So for some period of time and evolutionary biologist would have a hard time figuring out if and when they became different species, if they only use the BSC.

Q. Is there a gene for homosexuality?

A. There is no evidence of such a gene, and also only little evidence that homosexuality is heritable in a significant way (e.g., most homosexuals being born from heterosexuals, but see comment by uyedaj below). That doesn't mean that homosexuality is a choice, any more than heterosexuality is ("when did you choose to become heterosexual?"), but it is not likely tied to any specific gene. That said, we don't know what determines our sexuality.

Q. How come there are no other species as intelligent as we are?

A. Why would you expect other species as intelligent as we are? I have been thinking about this for a while, and one answer has to do with competition between species who share similar niches, which is conceivable when they are both intelligent humanoids. Neanderthals were probably pretty intelligent, more so than any other non-human animal (had slightly bigger brains than we do, though that doesn't imply higher intelligence).

Another answer may be that someone has to be the most intelligent. You could equally well ask why there are no animals as fast as the cheetah, or why no other animals has trunks as long as those of the African elephant. You would perhaps be somewhat amazed if there were two different species who were equally fast and faster than all others. That would be some coincidence, no?

Yet another reason could be that it may be really difficult to evolve to our level of intelligence. Perhaps it is short of a miracle that any species are as intelligent as we are. Maybe there is life on many other planets, but it is super rare that any of those species are more intelligent than a pig. I don't think that is a likely answer, but we don't know.


  1. Wow, you're famous! Great stuff.

    1. Hardly famous, but it was a rewarding experience.

  2. "No evidence" for heritability for homosexuality is too strong. There are several twin studies that show some heritability, usually not very high, but I believe they are significant (sorry I'm feeling lazy and am not looking them up). However, I'd say there is no more a gay gene than there is a "height gene" or a "thinking gene". The traits are almost certainly caused by hundreds of loci, and singling out one gene in a complex developmental pathway that leads to a trait as the causative factor is a fool's errand. A gene that causes something in one genetic background may not do the same thing in another person. Think of genes as a set of directions telling you how to get somewhere. One of those genes says "go west 100 miles". Where that leads you depends on the directions given by the other genes, and hence, no single gene can be credited for where you end up (although the trait may still be very much genetic, and some alleles might often lead you to end up in the pacific ocean).

    1. Yes, fair enough. Too strong to say that there is no evidence for homosexuality being heritable. Amended.

  3. For someone who has been hammering the "chicken and the egg" meme for so long, this question must have been the most rewarding for you.


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