This Week in Evolution

Not enough people voted on the Reader’s Choice, so this week’s paper is “Phylogeny and geography predict pathogen community similarity in wild primates and humans” by Jonathan Davies and Amy Pedersen, published in Proceedings of the Royal Society.

Many humans diseases, from flu to AIDS, come from other species. Similarly, diseases from dogs are an increasing threat to lions, while cat diseases kill sea otters. Are there general rules that predict how likely two species are to share diseases?

To find out, the authors analyzed several large data sets on diseases of humans and 117 other species of primate (apes, monkeys, etc.). They hypothesized that species are more likely to share diseases if they live near each other and/or if they are more closely related, that is if they share a more recent common ancestor. This is similar to how we define relatedness in humans: brothers and sisters have more recent common ancestors (parents) than cousins do (grandparents). Fortunately, the family tree for primates is relatively uncontroversial, at least among scientists.

Continue reading "Sharing diseases with relatives and neighbors" »

Posted by R. Ford Denison at 06:53 PM | Permalink | Comments (0)

Three recent papers in Proceedings of the Royal Society discuss differences between males and females or, in one case, among males.

“The costs of risky male behaviour: sex differences in seasonal survival in a small sexually monomorphic primate” by Cornelia Kraus and others, is based on a 10-year study of differences between male and female behavior in grey mouse lemurs. During the breeding season, males had lower survival than females, despite any possible risks associated with pregnancy or raising young. The higher risk for males apparently resulted from their tendency to travel more, looking for females.

The sexes also differ in winter behavior: females hibernate, while males remain active. Is there something about female physiology that makes hibernation healthier for them than it would be for males? Maybe, but there was no difference in winter survival between the sexes, which don’t differ much in size in this lemur species. The authors suggest that hibernation might have longer-term benefits in females, such as increased lifespan, whereas males need to stay active to bulk up in preparation for the breeding season.

This paper reminded me of an earlier paper on albatrosses, in which "in each pair, the male spent the winter just north of the pack ice in Antarctic waters whereas the female stayed south of Madagascar." It’s not hard to understand why males and females might differ in various ways (size, color, etc.) but differences in behavior outside of the breeding season are more interesting.

The second paper addresses an old argument between Charles Darwin and Alfred Russel Wallace, who developed similar explanations of evolution by natural selection at about the same time.

Continue reading "Separate vacations and other sexual differences" »

Posted by R. Ford Denison at 11:02 PM | Permalink | Comments (2)

Two papers this week may shed some light on human evolution. We aren't descended from modern monkeys or lemurs, but we can often learn something about our ancestors by studying our distant cousins.

Continue reading "When did social learning evolve?" »

Posted by R. Ford Denison at 04:59 PM | Permalink | Comments (0)

This week's paper is "Do capuchin monkeys (Cebus apella) use tokens as symbols?" by E. Addessi and coauthors, published in Proceedings of the Royal Society.

Humans use symbols in various ways, from drawings that somewhat resemble the object represented to national flags and religious symbols that represent complex ideologies (or at least group identity). Is symbolic reasoning a uniquely human trait, at least on this planet?

Continue reading "Money for monkeys" »

Posted by R. Ford Denison at 06:31 PM | Permalink | Comments (0)

I have written about evolutionary trade-offs before, starting with early posts about trade-offs between seed size and seed number in plants, and trade-offs between the ability of insects to escape predators by flying away, versus the ability to hide from them by playing dead. I have also given some examples of the increasing use of sophisticated experimental (often molecular) methods in evolutionary biology. This week's paper combines both themes.

The paper is "Restriction of an extinct retrovirus by the human TRIM5-alpha antiviral protein" by Shari Kaiser, Harmit Malik, and Michael Emerman, published in Science (vol.316 p.1756).

Retroviruses are made of RNA, but make DNA copies of themselves that can insert into the DNA of host cells they infect. HIV, the cause of AIDS, is a well-known example, but there are many others. If DNA copies of the retrovirus are inserted into cells giving rise to sperm or eggs, they can be passed to the next generation, as endogenous retroviruses. If the DNA inserts somewhere where it turns an important gene on or off, it may kill the host. Or, once in a while, this change may turn out to be beneficial. The few beneficial changes are the ones that survive and spread, just as the few mutations that are beneficial are the ones that persist.

VWXYNot has an interesting discussion of how a creationist web site misused one of her papers as evidence of "intelligent design." She shows how shared endoviruses can be used to infer shared ancestry, providing yet more evidence that we share a recent ancestor with apes, less-recent ancestors with monkeys, etc. But that's not what this week's paper is about....

Continue reading "Trade-offs in defense against retroviruses" »

Posted by R. Ford Denison at 08:28 PM | Permalink | Comments (4)

Two related papers this week: “Savanna chimpanzees, Pan troglodytes verus, hunt with tools” by Jill Preutz and Paco Bertolani, published in Current Biology (17:1-6), and “4,300-year-old chimpanzee sites and the origins of percussive stone technology” by Julio Mercader et al., published in Proceedings of the National Academy of Science (104:3043-3048).

Preutz and Bertolani report field observations of chimpanzees in Senegal making simple wooden spears and using them to kill bushbabies (sleeping in hollow trees) for food. Several individuals were seen making and using the spears, although apparently they only saw one successful “hunt.”

Continue reading "Teenage chimps with spears and hammers" »

Posted by R. Ford Denison at 03:41 PM | Permalink | Comments (10)