Anne writes:

Drs. Racaniello and Elde,

What an enjoyable, educational episode!  Dr. Phadnis’ recounting of the history of the work that preceded his own, and his own work, made this podcast an engaging one (I wish there had been a few slides to accompany his talk, as it would have enhanced my understanding of the gene interactions – but I’ll take a look at the paper).  Dr. Phadnis’ storytelling style reminded me of Eric Landers’ way of teaching, as he interweaves the history of science into his lectures (I’ve taken the excellent MITx Biology course he teaches).

Thanks for these fine episodes!  Will you be building a ‘library’ of recommended books and videos for this podcast, as you have done for TWiV?  It would be great to be able to explore some of the books on the topic of evolutionary biology and its intersection with genomics and genetics.



Alex writes:

Hi Nels & Vince,

congratulations on another fascinating addition to the “This week in” franchise. . . its another beautiful day here in White Salmon, Washington, 16 Celsius and sunny, Mt Hood brilliant with spring snow . . .

Speaking of snow and ice, in episode 1, Nels mentioned in passing a colleague named Joe Thornton, a biologist and amateur hockey player (with the monicker of a very celebrated pro) who was proud of leading his men’s league in penalty minutes.

As it happens, penalty minutes have been used as a source of data on aggression — penalty minutes for roughing and fighting are a convenient metric for non-pathologic aggression– and are associated with more extreme (2D:4D) finger length ratios ( a marker for fetal exposure to androgen, which is presumably the cause of the altered behavior).

On hockey teams, there will always be one or two tough guys— there have to be, or the team will be abused by competitors. But a team composed entirely of tough guys is no good either. Instead, coaches balance a team for toughness and skill, but that’s all done quite consciously. Evolution, here, appears to have produced an epigenetic mechanism for modulating individual behavior, but to be useful that behavior would have to be modulated within the context of other individuals. While it’s easy to see how you might get a gene that makes an individual more aggressive— a gene that instead means that individual behavior could be epigenetically tuned is harder to understand.

Where should one look for genes which would control the distribution of traits in a population as a coach does in assembling a team? EG not the chance that an individual might have a trait or not, but a “meta gene”, one that would control, say, the skewness or kurtosis of the distribution of such traits? Have any such genes been found?

Many thanks for another great podcast,


William writes:

Dear TWiEVO Nels and Vincent;

Here in Berkeley, CA, it is 55F/13C, and in the past day and a half we have had a glorious 1″ / 2.5cm of rain – something like 3.5-4% of our normal annual total, which we have not seen for several years!

While listening to the great TWiV 382 with Ed Chuong and Nels as guests, toward the end, in a letter, the Comb Jelly came up (it’s anus having just been discovered). There was general “hum, that’s interesting” but to my surprise neither Nels or Vincent commented on the (considerable, it seems to me) evolutionary significance of the Comb Jelly: It appears to be a rare instance of complex biological elements having been created in parallel with the main stream of evolution and not captured and reused. (As opposed to the central retrovirus of TWiV 382, which seems to illustrate the parsimony of evolution: If there is something close to what I need, I will grab it and shape it to my needs rather than reinvent it. (With apologies to Vincent for such anthropomorphizing.)

I snipped this from “Evolution, You’re Drunk – DNA studies topple the ladder of complexity.” BY AMY MAXMEN  (  a couple of years ago, which is a popular science commentary on “Ryan, J., et al. ‘The genome of the ctenophore Mnemiopsis leidyi and its implications for cell type evolution.’ Science 342 (2013),” and which seems to capture the key point:

“Late last year, the animal evolutionary tree quaked at its root. A team led by Joseph Ryan, an evolutionary biologist who splits his time between the National Genome Research Institute in Bethesda, Md. and the Sars International Center for Marine Molecular Biology in Bergen, Norway, analyzed the genome from a comb jelly,  Mnemiopsis leidyi, a complex marine predator with muscles, nerves, a rudimentary brain, and bioluminescence, and found that the animals may have originated before simple sponges, which lack all of those features. (Ref to the Ryan Science

“If comb jellies evolved before sponges, the sponges might have lost the complexity that the ancestor uniting them and comb jellies possessed. Or, that ancestor—the ancestor of all living animals—had the genes to build brains and muscles, but did not form those parts, and neither did sponges. If this is true, then comb jellies deployed the genome they inherited to build a brain, nervous system, and muscles, independent of other animals. There’s some support for this possibility: A unique set of genes seems to underlie comb jellies’ muscles.

“Both hypotheses run counter to scenarios in which organisms evolve to be increasingly complex. In one, a complex nervous system and muscles were lost in the sponges. In the other, the sponges had the genetic capability for complex features but stayed simple, while a more primitive group, the comb jellies, acquired brains and muscles that help them chase down prey. Furthermore, the idea that complex parts like a brain and nervous system—including nerve cells, synapses, and neurotransmitter molecules—could evolve separately multiple times perplexes evolutionary biologists because parts are gained one at a time. The chance of the same progression happening twice in separate lineages seems unlikely—or so biologists thought. “Traditional views are based on our dependence on our nervous system,” says Ryan. “We think the nervous system is the greatest thing in the world so how could anything lose it,” he says. “Or, it’s the greatest thing in the world, so how could it happen twice.”

Anyway, it seems that a TWiEVO that looked at this general issue (and maybe this specific research) would be interesting.

William (Bill)

Berkeley, California

Jeff writes:

Please put TWiVEO on Stitcher.

By the way, I am an American computer programmer living in Medellin Colombia – City of Eternal Spring. The weather here is always low 80’s during the day and low 70’s at night.

Adam writes:

Dear Dr Racaniello and Dr Elde,

Recently, I came across an interesting concept but I wasn’t sure how to explain it in terms of molecular biology. Many animals possess certain instinctive behaviours, such as: baby turtles running straight to the ocean after hatching, nest building by birds, cuckoos pushing other eggs out of the nest and avian seasonal migration.

While I can appreciate the evolutionary advantages of such behaviours, I wonder how these behaviours became instinctive in the first place. Was nest building once a learnt behaviour, then became an instinct? If so, how are such complex behaviours passed down – genetically? Was a transition from certain learnt behaviours to instincts gradual, and how is this reflected in the changes of animal’s genetic/epigenetic make-up?

Thank you for sharing your knowledge and expertise on so many platforms!

Greetings from sunny Manchester, UK.!

Cheryl writes:

Please gentlemen, I beg you, create podcasts more frequently! I’ve turned many of my colleagues onto the programs and they’ve all commented on how they love them all, but wish you’d do more frequent evolution podcasts.

We also would love to have some evolution topics that could be used in the high school classroom, to supplement class lecture.

Thank you to all the twi crews for the fantastic podcasts!


World History Teacher

William Horlick High School


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