Do females really select the best penis to mate with?
… Come on.
Hi Guys, Crystal here for DNews.
Ready to talk about penises?
Well Harvard scientists working with international collaborators have discovered that the penis
of a Caribbean lizard may be evolving faster than their other physiological traits.
This is a result of sexual selection that contributes to genetic as well as genital
diversity in the species and leads to questions as to why this occurs:
Do females, who have the power of mate choice, select the “best” penis for them?
Or, is this diversity the result of a sexual arms race with male lizards looking to reduce
female control of reproduction?
Well, lets get into the dirty details.
Lizard penises are different from human ones.
For one thing, male lizards (and others in the order Squamata) don’t just have one
penis, they have a pair of organs called hemipenes.
Don’t get too excited, they usually only use one at a time, and hemipenes means “half
penis” so … Anyway, these organs are kept inside the body for day to day activities,
and then one becomes externalized by erectile tissue for reproductive purposes.
The scientists who performed the study used comparative methods to ask whether there was
more variability in hemipenis shape (length and width), than of non-genital traits like
limbs and dewlaps - a flap of skin under a lizzard’s throat.
This is an important question to answer because increased diversity would imply an increased
evolutionary rate for genitalia.
To ask this question, scientists examined hemipenes and body morphology from 5 samples
of 25 species of Anolis lizard in an attempt to represent the “diversity of microhabitat
specialists in the Caribbean anoles”.
What they found, when they compared measurements is that many very closely related lizards
have hemipenes very different from each other!
Scientists were able to calculate the rate of change necessary to produce such different
genital features and put this information in the context of a relative lack of diversity
in limbs and dewlaps to conclude that the genitalia of caribbean Anoles lizards evolve
approximately six times faster than other morphological traits.
Genitalia is frequently used to differentiate similar species, but no one has done a quantitative
measure of increased evolutionary rate until now.
And the speed of evolution is so different that it begs the question, why?
Well, the scientists who performed this study assumed that the rapid evolution of male genitalia
was a result of co-evolution with the female and proposed two hypotheses: either the evolution
occurred through “cryptic female choice” where females drive selection through personal
preference, or “sexually antagonistic coevolution” an attempt on the part of male lizards to
reduce the female influence on reproduction.
More studies are needed to determine which of these is happening here, but what do you
think?
Subscribe to DNews and let us know your thoughts in the comments down below!
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What do you think?
Inexplicable female choice or sexual arms race?
Let us know in the comments down below.
And you can come find me on Twitter @PolycrystalhD