Males taking pregnancy to a whole new level

There’s an interesting debate going on in the science communication community over whether it’s more valuable to talk about relevant science news or cool science news. If you read my tagline, you’ll know which side I’m on (though my preference is for science news that are both relevant and cool). But just for today, I’d thought I’d switch roles and share the findings of a recent article on a topic that definitely doesn’t seem relevant for us: male pregnancy.

Male pregnancy occurs only in seahorses and their relatives, and happens when females deposit their eggs in a pouch located on the male. The pouch serves a similar function as the human uterus and provides nutrition and protection for the offspring while they develop. In a recent study published in Nature, researchers looked at how male pipefishes manage these pregnancies and find surprising behavior.

First, the researchers confirmed that the male pipefish prefers to mate with larger females. This maximizes evolutionary fitness (survival of the fittest) because larger females lay more eggs and their eggs have a greater chance of surviving. Interestingly, the shorter the male, the stronger the preference for a large female. I’m going to let you draw your own conclusions as to the origins of Little Man Syndrome.

Second, the researchers found that the chances of survival of the offspring depend on previous pregnancies. If a male really invested himself in a previous pregnancy and spent a lot of energy caring for the offspring of a larger female, the chances of survival of a later pregnancy from a smaller female are much lower. This essentially means that the male can gauge the “attractiveness” of a female and distribute his resources accordingly. In some cases, when forced to reproduce with a small female, males can partly or even completely abort the offspring (by not spending energy for their nutrition and care) to conserve their reproductive potential for when they hit the jack pot chunky female. Kind of a blow to the supermodels of the pipefish world, if you ask me.

Overall, the study suggests that male pipefishes have much greater control over reproduction that we initially thought, and certainly much greater control over reproduction when compared to the standard female mammal pregnancy scheme.

Now let’s see if we can find some relevance to this study and make it a two-for-one. Can you find any relevance for us in this study, in aspects of the study, or even in questions it raises? Contribute your thoughts in the comments!

Pipefish

Reference: Post-copulatory sexual selection and sexual conflict in the evolution of male pregnancy. (2010) Paczolt KA, Jones AG. Nature 464(18):401-4.

How old is compassion?

I recently wrote about natural selection, or the survival of the fittest, in bacteria, which is a pretty ruthless process. When it comes to humans, I’m thankful that we care for the sick and the disabled. Having had a few common health issues myself, I know that in the wild, I probably would not have made it past 15 or 16 years old (ever had mono? I can’t imagine hunting mammoths with mono). That being said, I always assumed that compassion and care for the ill was a relatively new concept, made possible by advances in civilization. A new paleopathology (that’s the study of past diseases) finding suggests compassion may have much earlier roots.

A group of Spanish bone hunters found a very interesting cranium at the Sima de los Huesos site in Spain. The cranium belongs to a child who died between the ages of 5 and 12 years old and who lived at least 530 000 years ago! The cranium has been almost fully reconstructed and clearly shows many signs of malformations. The researchers were able to link those signs to a disease that still exists today called craniosynostosis. This disease can have multiple causes and results in cranial deformities (such as an asymmetrical face) and mental retardation. In this case, the pathology would have been present before birth. So what we have here is that 530 000 years ago, there was a child who was visibly abnormal and affected in a way that he or she probably would not have been able to keep up with the group. The amazing finding of this paper is that this child made it to be at least 5 years old, and probably closer to 10 years old. This suggests not only that the population did not act against the individual who was different or sick during infancy (i.e. they didn’t kill a sick baby, like some other populations have been known to do), but also that they cared for the disabled. Not something I would have expected of our hunter-gatherer ancestors.

An interesting question that springs to mind here is, if humans from the Neanderthal era showed some form of compassion, what about animals? I’ll definitely be keeping my eyes out for more research in this area. This kind of science is my favorite: answer a question, and many more arise (unless we’re talking about my thesis project: in that case, all I want are answers).

As I mentioned, I always thought that caring for the ill was a very recent human behavior, but now I’m not so sure. In any case, I’m just glad to know that our ancestors were not complete jerks.

Image of the cranium from the original article
Gracia A. et al, Craniosynostosis in the Middle Pleistocene human Cranium 14 from the Sima de los Huesos, Atapuerca, Spain. Proc Natl Acad Sci USA, Mar 30 2009.