Hello world
I am thrilled to start cross-posting on Panda's Thumb (from my small corner of the internet at mathbionerd.blogspot.com). I'm an evolutionary biologist studying many things, which generally involve sex-specific processes (sex chromosome evolution, meiosis, male mutation bias: http://cteg.berkeley.edu/~sayres). I am dedicated to communicating science in language that is accessible to general audiences. So, here I'll be posting "accessible research", as well as other bits about science careers.
39 Comments
Nick Matzke · 11 April 2013
Yay Melissa! New blood is a great thing!
diogeneslamp0 · 11 April 2013
Sex chromosome evolution expert, eh?
Great. Let's talk about sex.
We've needed an expert on evolution of sex. You know creationists like Ray Comfort are always saying, "How did the male and female sex organs evolve to fit so well together?" (Of course, it is not clear that they actually fit that well together.)
I can guess the vagina evolved from the cloaca of amphibians. But seriously, how did the penis evolve? Penises are so... multifarious. They're not all homologous to each other. Obviously the penis of the barnacle or the flea is not homologous to that of tetrapods. So how DID it evolve? And if you know anything about the evolution of the vagina, that would be great too.
And throw in testes and ovaries while we're at it, if you know anything about it.
I mean I'm guessing that primitive vertebrates were like hermaphrodites, with male and female sex organs, and then there was a genetic signal so that some allowed their testes to atrophy, and others allowed their ovaries to atrophy. Or are testes and ovaries homologous, and just modified versions of the same sex organ, and our ancestor only had one set? If so, how did our vertebrate ancestors breed before they became derived.
I'm sexually confused.
DS · 11 April 2013
diogeneslamp0 · 11 April 2013
Richard B. Hoppe · 11 April 2013
Welcome, Melissa!
DS · 11 April 2013
M. Wilson Sayres · 11 April 2013
I think a great example of male and female organs evolving to fit so well (or unwell) together would be duck penises and vaginas. Rape is common in some species of water foul (would be difficult to argue why this was "designed"). As a result, some water foul have very long penises for forcing sperm into their unwilling mates. But, the some females also have vaginas that can squeeze tightly and sidetrack the penis to a dead-end (some females have three-pronged vagina, where two lead to nothing) to prevent sperm from reaching the right outlet for fertilization.
John Harshman · 11 April 2013
I wonder if it's possible that Todd Akin had heard about any of this. Ability to exclude unwanted sperm, to store sperm from different individuals in different places and for very long times, and to choose which sperm fertilizes one's eggs is a fairly widespread thing (though not, as far as I know, in mammals).
I'm not all that thrilled with your just-so story, though. Rape is very common in mallards (and most reports of duck rape come from that species), but the ducks with the extra-long penises are not mallards but stifftails, and I haven't seen any evidence that rape is more common in stifftails than in mallards.
Of course you all understand that none of this has anything to do with sex chromosome evolution, right? Melissa, if you're reading, I would really like a PDF of that BioEssays paper.
M. Wilson Sayres · 11 April 2013
You're right, John. That was an over-simplification for a quick comment, and I am not a duck researcher. Most birds don't have penises (apx 3% do). Mallards have penises and do engage in rape, as do stifftails. I don't know if anyone has tested whether length of a penis is correlated with the incidence of rape. Likely a combination of factors (drift, sexual selection, etc) contribute to penis length and morphology. I am happy to learn more about it, if you're willing to share.
Also, thank you for pointing out that penises and vaginas are not sex chromosomes. I have experienced that people often entangle the two. Even though genes on the Y are generally expressed in the testis and involved in spermatogenesis, I am not aware of evidence that genes on the sex chromosomes are (more often than genes on the autosomes) involved in the actual morphology of the sex organs. I am generally interested in all things "sex", but my expertise is in sex chromosomes.
Email me (mwilsonsayres at berkeley dot edu) and I'll happily send you a copy of the BioEssays paper.
harold · 11 April 2013
M. Wilson Sayres · 11 April 2013
Doh.. thanks :)
John Harshman · 11 April 2013
There is a bit of literature on this subject. Coker et al. 2002 found a relationship between frequency of forced extrapair copulations (i.e., rape) and penis length. Caveats: As with any comparative study involving either behavior or soft (sorry) anatomy, there are lots of simplifying assumptions and holes in the data set. And I wished they had standardized for body size. Also, there are various correlations among other factors that are hard to separate. They divide species into four classes: monogamous, rare FEPC, frequent FEPC, and polygynous/promiscuous. I'm not sure that's a clear scale; does polygyny really mean extra-frequent FEPC? But anyway, there is some evidence to support your story.
And there's a nice review of the subject in all birds: Montgomerie and Briskie 2007.
Coker, C. R., F. McKinney, H. Hays, S. V. Briggs, and K. M. Cheng. Intromittent organ morphology and testis size in relation to mating system in waterfowl. Auk 119:403-413.
Montgomerie, R., and J. Briskie. 2007. Anatomy and evolution of copulatory structures. Pp. 115-148 in Reproductive biology and phylogeny of birds (B. G. M. Jamieson, ed.), Science Publishers, Enfield, NH.
Karen S. · 11 April 2013
Welcome Melissa! Looking forward to your posts!
diogeneslamp0 · 11 April 2013
But what did the MAMMALIAN penis evolve from? Yes, I know developmentally it's a clitoris plus some androgens. But evolutionarily, what was it before?
Do all mammals even have penises? Platypuses? Marsupials? You say some birds have them, most don't. Are there some penises among tetrapods that are not homologous to other penises in tetrapods? There are so many sperm delivery appendages, it boggles my mind.
M. Wilson Sayres · 11 April 2013
As far as I know all mammals have penises, and there are some very curious things about them (esp monotremes and marsupials compared to eutherian mammals), which probably merit separate blog posts. Thanks for the ideas. I'll work on these, so stay tuned!
M. Wilson Sayres · 11 April 2013
Thanks for those references, John!
Ray Martinez · 11 April 2013
M. Wilson Sayres: I am dedicated to communicating science in language that is accessible to general audiences.
---Good; because those who don't will never educate or convert the public. When science hides behind jargon they are asking, nay demanding, that the public accept by blind faith. If science cannot convey its findings to the public in understandable language then these findings remain private or esoteric knowledge.
M. Wilson Sayres · 11 April 2013
Thanks, Ray! I am still learning the balance between content and accessible language, and may default to using simpler terminology, or simplifications, while still trying to get the real science across.
diogeneslamp0 · 11 April 2013
EvoDevo · 11 April 2013
EvoDevo · 11 April 2013
Paul Burnett · 11 April 2013
Flint · 11 April 2013
EvoDevo · 11 April 2013
Ray Martinez · 11 April 2013
M. Wilson Sayres: I am dedicated to communicating science in language that is accessible to general audiences.
---Currently there is a hot discussion occurring down-page, titled "Does CSI enable us to detect Design? A reply to William Dembski" authored by Joe Felsenstein. The claims of William Dembski are under scrutiny. But these claims are completely reliant upon advanced mathematics and algebra. Of course the refutations offered by Evolutionists are too. The point is: the public or general audience must take, on blind faith, the word of both camps. Dembski's theories stand no chance of affecting public understanding or changing the world.
---What happens, invariably, is that the interested lay public is kept corralled in their box out of fear of being branded ignorant by persons on both sides of the debate. Since this is a public forum has anyone in the above mentioned topic taken the time to create a post or two that explains the issues to anyone who is not an expert? And keep in mind the fact that the average lay person is indeed quite intelligent. So what is actually going on, in said topic, is that a handful of people are attempting to show-off and one-up each other. Someone needed to say that. So there. I did. And when the discussion is over the public is none-the-wiser, nothing has changed. Not only that, but the public can never become wiser because no one in the discussion took the time to explain in universally understood prose (like I am using here). Everytime the interested public clicks on the link, or when it comes up in a search, upon seeing the math or alegbra, away they go.
---I made a handful of short posts in the Felsenstein topic. Some of them were deemed off-topic and sent to the Bathroom Wall. But I would never participate in such a discussion for the reasons just stated. These discussions or debates are a complete waste of time unless the talents of the partcipants can explicate the issues so an intelligent on-looking public can understand. Absent these accessible explications, private knowledge is being practiced. "But most science cannot be dumbed down lest it suffer misrepresentation." Then it's not real science. Real science presupposes "take my word for it" and invalid "arguments-from-authority" to signify total illegitimacy.
---Neither Paley or Darwin employed any mathematics (yet when both men attended Christ's College, if I recall correctly, mathematics was required in order to graduate). Yet both produced theories that scientific men accepted and still accept. And these theories are widely cherished by the public. In closing, if the so-called experts are indeed talented experts then why can't they figure out a way to communicate their science---all of it, to the public?
fnxtr · 12 April 2013
"Think about how dumb the average American is. Half of us are dumber than that." -- George Carlin.
Rolf · 12 April 2013
Ray Martinez · 12 April 2013
EvoDevo · 12 April 2013
EvoDevo · 12 April 2013
Wesley R. Elsberry · 12 April 2013
Rolf · 12 April 2013
Henry J · 12 April 2013
Sex couldn't evolve until there were flowers and chocolate to use as bait.
Ray Martinez · 13 April 2013
Wesley R. Elsberry · 13 April 2013
Ray Martinez · 13 April 2013
Wesley R. Elsberry · 13 April 2013
EvoDevo · 14 April 2013
EvoDevo · 14 April 2013