Good morning all,
As I noted on Tuesday, we will not meet for lecture today. We have only one textbook chapter remaining, which we will save for our first meeting after the Thanksgiving break.
Instead of lecture today, I'll offer you a reading instead, one that encompasses several of our recent topics. In recent classes, we have considered the degree of cooperation and conflict between reproductive partners, as well as the signaling that occurs to influence each other. When sexual investment is strongly different between the sexes, we expect that sexual selection can drive exaggerated displays, enhance female 'choosiness' of mates, and promote unequal reproductive tactics. But, curiously, sexual displays also are common within pair-bonded species, in which males and females have equal (or nearly equal) roles and should be in cooperative agreement over parental investment, rather than in conflict. An explanation for this paradox has been lacking.
A very recent paper sheds some light on this problem, and present a mathematical model which supports the idea that inter-sexual signaling displays which originate to exploit a sensory bias in the signal receiver can evolve into a cooperative exchange, suggesting that sexual conflict can morph into sexual cooperation. This has significant implications for parental investment and care, as we've noted that the degree of sexual conflict is one of the primary drivers of sexual dimorphism in parental investment.
This paper was published in the Proceedings of the National Academy of Science (PNAS), our national body of 'science experts'. Election to the Academy is reserved for the top thinkers in one's field, and is a prestigious badge of honor. Their Proceedings journal publishes papers submitted by Academy members, as well as those that Academy members recommend for publication.
If you access this link from an IUP campus computer, you can obtain access to the full article and its associated material, through IUP library subscription. If you try to access the article from off-campus, you will be blocked. I've attached the PDF of the article, just in case.
The math of the authors' model is well beyond us. If we accept their model as being sound, it suggests that, instead of females being 'lured' into over-investment in their offspring by male displays, females instead evolve to require (or at least benefit from) the male display in terms of stimulating female condition/motivation to a level of investment which is optimal for the female (but less than that which is maximally optimal for the male). This causes males to remain invested in the pair-bond and their role in parental investment, and reinforces the pair-bond between mating partners. In a sense, the females are now requiring the males to remain present, remain attentive, and to offer displays, in order to ensure that their female partner is providing enough investment of her own.
As do many science journal, PNAS occasionally offers peer commentary on papers which are especially important, or especially difficult (this one is perhaps both). The associated commentary on this paper (link below, PDF attached), describes this result in the context of dove mating pairs, for which male stimulation of female reproductive condition is a well-understood and very necessary component to the reproductive cycle. Interestingly, as the commentary notes, the capitulation of this male-female exchange may ultimately be female self-stimulation of reproductive condition, a result which has been suggested to occur in doves. That may be the current evolutionary end-point to this exchange, but it also has the potential to serve as a type of an "escape clause", which males may now be selected to exploit. It would be interesting to see how much variation exists in this end-point, and whether males can benefit from females which perform more of their own reproductive stimulation.
I hope that you find this article interesting - it represent a nice, theoretical treatment of a difficult (= interesting) problem, and should set the stage for experimental work to come.
I hope that you all have an excellent Thanksgiving break - please be safe, rest, relax, eat, and enjoy. See you early in December for our last chapter.