Strolling with a skeptical biochemist
It's pretty unlikely that Ziya has genes to make testes - she is almost certainly lacking SRY gene.
Very well answered. Very logical... as it should be when explaining things like this to the general public. I applaud you.
I saw that one, good show Larry!
It dropped out before the end but the answer you gave up to that point agreed with my limited understanding. That is, we all started off female. Just some of us are a bit twisted.
Men have nipples because there is no selection against them having nipples?You adaptationist you!;-)
Congrats, Larry, you've hit the big time now!:)Deb(This may totally give away the fact that I haven't watched that show for a long time...but what happened to Jay Ingram?)
DK says,It's pretty unlikely that Ziya has genes to make testes - she is almost certainly lacking SRY gene.Ziya has all the genes required to make male body parts including those needed to make testes. The one thing she lacks if is the ability to turn on those genes at a specific time during development. Part of the reason for that is she lacks the transcription factor encoded by SRY—one of the few genes on the Y chromosome.
We didn't all start off female. We start off undifferentiated and our reproductive tissue and external genitalia take divergent paths. It is true that the undifferentiated external anatomy looks a bit more female but this is not the same thing as female. Think of wrasses. They (mostly) go through three sexual phases, undifferentiated juveniles, then female, then male. The juveniles would be insulted if you called them female.
Larry, thank you so much for choosing to feature the Carnival of Evolution logo in the interview. It smacks of expertise in evolution.
Bjørn Østman thanks me for advertising Carnival of Evolution but I might think twice about doing it again since he adds the following disclaimer to his posting ... :-)P.S. This post is not an endorsement of Larry's statements about why men have nipples.
I wanted to remain neutral on the nipple-question in that "official" post from the CoE admin.But, personally, I can say that while I trust nipples are a developmental leftover, I don't feel so sure that the reason they are still there is just because they aren't harmful and aren't selected against. It may be they can't be lost (e.g. to drift) in males because they are linked to some other developmental or physiological process in males. You know, pleiotropy.
This is actually quite simple - the reason that men don't have full-size fully functioning breasts is because we would spend all day playing with them.
If mammary gland is restricted to fetal sexual development, i don't think babies (including males) will lactate, but they do. http://en.wikipedia.org/wiki/Witch's_milkhttp://en.wikipedia.org/wiki/Male_lactation