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ResearchBlogging.orgHUMANS CAN live to over seventy years old, yet female fertility begins a precipitous decline after about forty years of age. This is unusual since most other species continue reproducing into old age. Some have proposed our extension of life past reproductive years is due to a survival benefit for grandchildren with grandmothers who contribute to their care. However, this benefit is not enough to explain the initial cessation of reproduction.

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ResearchBlogging.orgIN THE PAST week or so I’ve been writing about the attine ants, which have a complicated mutualistic network combining cultivated fungi and actinomycete bacteria, and are parasitized by Escovopsis fungi and perhaps black yeasts as well! Today I’m writing about the attine ants again, but along a very different angle. In this case this paper examines the influence of evolution upon reproductive behavior. I actually ran across the paper by accident, having previously planned to write about a paper on evolution and reproductive behavior in humans. This paper nicely transitions between these two themes.

Among organisms in general it is a bad idea evolutionarily to abandon breeding in favor of helping another individual raise its offspring. There are examples of social cheaters among groups as different as myxobacteria, slime molds, vertebrates, and insects. The myxobacteria and slime molds are bacteria and eukaryotes respectively that have converged upon a similar lifecycle. These are organisms capable of lone existence, but which mass together during unfavorable conditions to produce a stalk that launches spores. Ideally every strain in the group will be represented equally in the spores produced, but some cheater strains are able to produce more than their share of spores. Among vertebrates, there are examples in many groups of species that parasitize the nests of others, foisting off their young upon an unsuspecting individual. Cowbirds and cuckoos are well known among the birds, and cuckoos gave their name to the cuckoo catfish, which parasitizes cichlids. A similar parasitism is seen among insects where some wasp species will infiltrate another species nest and lay their eggs. The ants take this type of parasitism even further, with some species going to war against others to capture their larvae, which are raised in their captor’s colony and tend their brood. But the type of reproductive cheating occurring in attine ants is different from all of these!

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