Anthony writes:

There was a mention of living fossils in the recent TWiEVO.

The PDF attached is a paper about ants in amber found in Central New Jersey.  There are photos starting at page 10.  The fossils are some 90 million years old.  

Something very similar might be still seen today in any backyard.  The Hadrosaurus followed very much later by mammoths were definitely more impressive NJ residents.  Both are very long gone.  What might it be about the ants that allows for their continued success whether dinosaurs, giant mammals or trucks dominate the landscape?

The seemingly changeless nature of ants perhaps is what prompted Dali to feature them frozen in amber in Persistence of Memory.

Thank you.


Your speculation of conquest of the Neanderthal — along the lines of the fall of Troy — certainly is as good as any other.  On TWiV, Professor Despommier has posited that Neanderthals were exterminated by our diseases.  I’d wonder about the climate change of the time.  This definitely enabled the spread of Homo sapiens.  Why not other organisms from Africa?  These may have been vectors of diseases that our species grew up with.  The Ice Age specialized Neanderthals would have had no resistance.

Justin writes:

Dear Nels and Vincent,

I am loving this new podcast. I am a post-doc at Texas A&M University. I just finished my PhD work in Utah, and listening to Nels talk about Salt Lake makes me feel somewhat nostalgic and homesick. The University of Utah really is a fun place.

I have a question about TWiEVO episode #8. I may have missed something, but early on in the episode there was some conjecture about the inter-species interactions that resulted in Neanderthal genes making it into the human genome. Some of these conjectures assumed that rape, kidnapping, and the like may have been the primary drivers of this inter-species mixing. Is there any way to know, either by looking at sex chromosomes or even mitochondrial DNA, if the Neanderthals that contributed to our genome were predominantly male or female? If we knew the answer to this question, it would give us some very good hints about how all this actually happened.

I also have a listener pick. I just happened to be reading Endless Forms Most Beautiful: The New Science of Evo Devo and the Making of the Animal Kingdom, by Sean B. Carroll on the same day I was listening to TWiEVO #6, the episode on butterflies. It is a fantastic book and is very fun to read… especially if you really want to think about the nuts and bolts of how evolution works in animals.  I also thought it really complimented the discussion in your podcast.

Keep up the great work,

Anthony writes:

Darwin mural restored

I believe that the mural has been restored.

Yet another interesting image brought to Facebook by Kim Dallesandro.


Trudy writes:

Dear Vincent and Nels,

During my daily perusal of the Internet for cool science, I came across an editorial in Nature, which talks about modern gene-editing tools and how they’re used to understand the mechanisms of evolution.  Of particular interest to me was the attached paper by Nakamura et al. Apparently these guys (and gals) used CRISPR–Cas9 to inactivate the genes involved in zebrafish development, producing animals having fin tips more like the feet and digits of land vertebrates.  I can already hear the anti-GMO crowd and creationists chomping at the bit.  Might make for an interesting snippet for a future episode?

Thanks for all the work you do!


Geoffrey writes:

Drs. Elde and Racaniello:

This episode inspired several questions. Unfortunately, this seems to have been a case where knowing how to ask a question is important. I was only able to find partial answers to my questions and was hoping that you gentlemen might find them worth asking as well. These questions are kind of long. If you do use my questions on an episode, then feel free to use only the ones you have the time to use.

1) You mentioned the PRDM9 is known to be responsible for some forms of mammalian sterility. Might it also be responsible for lowered fertility?

This is the question that I was able to answer because I figured out that I was asking the question at the wrong point in the fertility question. I was wondering if recombination mismatching might be causing reduced successful fertilizations in some couples that wouldn’t have occurred if they were coupled with different partners. However, I realized that the answer that you gave on the show was pretty much the answer as far as PRDM9 goes. PRDM9 operates at the the meiosis stage. Thus, any PRDM9 effect should result in a defective haploid (especially sperm) and lowered fertility to sterility with all partners rather than partner-specific reduced fertility.

2) Have there been studies on the genetic phylogeny of the origins of PRDM9?

I found a partial answer for that. I didn’t find any information on PRDM9 prior to mammalians but I did find that it occurs in metatherian (non-placental) mammals (specifically platypuses). Perhaps as one might expect, platypus PRDM9 is significantly different from any other extant eutherian PRDM9.

However, I was still not able to find out theories (or evidence) on the origin of PRDM9. Do you know what the leading theories are? Was it a radical repurposing of pre-existing zinc finger system? Was it a gift from a retro-virus?

3) You mentioned that meiotic recombination mutation rates are lower than the theoretical limits suggesting a control mechanism about which we know little or nothing – yet. Is there any evidence that this mystery control mechanism could become deregulated under certain types of stress on the organism? If this happened, then it could allow for higher mutation rates (a form of hypermutation) and, thus, potentially faster genetic adaptations in times of environmental stress.

4) In a more general question about sex and meiotic recombination – Is there a single main control system for this process across kingdoms? Have different mechanisms for meiotic recombination arisen independently? Have we been able to develop a genetic phylogeny for meiotic recombination system and do we know how they arose?

Thanks for the thought-provoking show,

Geoffrey Tolle

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