Chaim writes:

Hi Professor Elde,

As far as B cell evolution goes, I’m with Dave. B cells are indeed the relevant ‘organism,’ and the fact that you don’t pass your evolved B cells to your children is irrelevant. In this sense, the B cell does, in fact, have “its own germline” – a unique V(D)J rearrangement with somatic hypermutations that is passed down to its daughter cells but cannot be transferred to an “unrelated” B cell (by which I mean one descended from a different naive B cell, with its own unique rearrangement). Moreover, while it is of course precisely this “germline” on which most selection acts, changes can accumulate in other portions of the genome that also increase reproductive fitness -otherwise known as a lymphoma. Cancers evolve, too, at least by this way of seeing things.

Whatever we call it though, thank you for an always insightful and interesting podcast. I look forward to it every month.



(a computational immunologist specializing in B cell evolution)

DB writes:

Nels and Vincent, I just received my second dose of the Pfizer vaccine.  For about the first 12 hours after the injection, I felt a little buzzy or giddy.  Several associates reported feeling similarly.  It brought me back to the rats and the analgesia papers that were previously discussed:

I am just wildly speculating here, and I have no idea if the spike produced by the vaccine could get in the bloodstream, but what a story if somehow early in the infection, the virus actually made you feel good?  Maybe you want to go out, maybe to the bar with your friends and maybe you’re a little more talkative than normal.  Meanwhile you have pre-symptomatic transmission going on.  Sure would be a good outcome for the virus.



Cathy writes:

Dr. Elde-

My dentist and I have had a long ongoing conversation about the disappearance of “wisdom” teeth aka first molars (M1) in the human jaw. He explains that the loss is genetically driven to accommodate the decreasing size of our jaws due to changed mastication needs and growing brain size. 

The question I have is: how is it that the genetic loss of wisdom teeth is asymmetrical?  Many individuals only have three first molars and are missing one from either side. Doesn’t the fetus start out as a flat pancake of sorts that curls together and binds down the center of the face? How does one side loose the first molar and the other side retain it genetically?

Thanks for clearing up this evolutionary questions!


Ingrid writes:

Dear Nels and Vincent,

I don’t manage to catch every single episode of TWiEVO I’m afraid (my loss!) so maybe you’ve covered or referred to this topic in an earlier episode – if so please let me know which one.

The genome of this plant is so weird that they can’t figure out how or why it got that way! It’s lost an amazing amt of important functional dna yet has a huge genome that is so ‘repetitive’ and full of sequences kidnapped from long-ago and now extinct hosts that it was very difficult to analyze. I doubt I will understand it even if and when you do go over the referenced papers or the topic in general, but I would love to listen anyway!

My husband and I used to be avid desert wannabe botanists out here in desert areas of the western US, and there is an extremely tiny-flowered parasitic plant – Pilostyles thurberi – that up to recently was included in the same plant family as Corpse flower (Raffelesiaceae). So that anomaly is always mentioned in the few plant books that include this tiny parasitic plant, which is how we came to look up Corpse Flower. 

Sadly (to amateur wannabe botanists!) in the last 20 years or so this tiny desert parasitic plant’s family has been split out of the Raffelesiaceae. Its new family (Apodanthaceae) is even in a different order from the Malpighiales order that Raffelesiaceae is in – Wiki claims Apodanthaceae is in Curcurbitales, but the Jepson Manual says order attribution is still unresolved and could be either Malvales or Curcurbitales. (the Jepson Manual contains the definitive scientific descriptions of all CA plant species, and the online version is constantly updated with the most recent scientific consensus) 

Popularly, online and among amateur botanists the two plants are still thought of as being closely related, one having the largest flower of any plant and the other close to the smallest.

Either way, I would love to see someone figure out the genome of the tiny desert parasite, and see if it is maybe even bigger than the giant Corpse flower genome with similar anomalies!

Thanks for all the great TWiEVOs, TWiVs, TWiPs, Immunes, etc.

I love everything about the way you do these podcasts.

So great to ‘hang out’ with all you scientists and listen to real, fun, people talking about science.

You have helped me get through this last year with its dearth of social interaction and reduction of classes, lectures etc.

But I’m not a temporary viewer just til the pandemic is over! Will be relying on you guys for the duration, so please keep it going!


Larry writes:

Drs Elde & Racaniello:

…On the other hand, you’ve also probably already seen this, in which case, skip this letter.

This article

from today, May 4th, has links to the three papers and one editorial in Science (April 30th) about some unusual bacteriophages, as the link indicates:

It turns out the 1977 discovery of an alternative DNA-coding scheme, substituting 2-aminoadenine (Z) for the usual adenine (A) was not a fluke: there are more examples.

I believe you’ve commented recently on how the difficulty of culturing in a lab affects what gets studied, and this is another example of that.

Plus, Z is one of the amino acids found in meteorites, which should be the basis for a 1950s-style science fiction film, “Bacteriophages from Spaaaaaaaaaaace!”.

No insightful questions from me, just “ZTCG!  wow!” … and “Would PCR be impeded by appearance of Z instead of A, so we’d never know this kind of bacteriophage was present in samples?”

Thanks as usual for your truly interesting and informative discussions,


Life-long 🙂  TWiEvo follower – Software fan-boy in San Diego, where it’s 74℉ / 23℃ at noon on May 4th