VOLVOCINE ALGAE have a recent evolution of multicellularity, only 30-70 million years ago. This may produce a better record of the early history of this process than we have for other multicellular organisms. Metazoans and multicellular plants evolved over 550 million years ago (multicellular plants multiple times, and some suggest a very ancient history of multicellular algae over 800 million years ago). The fossil record for fungi is not very good, but unambiguous multicellular fungi were present by 500 million years ago. Bacteria meanwhile beat everyone out by evolving multicellularity several times perhaps 2-3 billion years ago. Since most multicellular organisms have a distant origin, extinction has eroded the base of their evolutionary trees so that the details of the transition are hard to extract. The volvocine algae have a much more recent history of multicellularity, and we have been able to determine much about their evolutionary history from phylogenetic studies of these algae and their relatives.

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ABOUT A MONTH ago I reported on a better-resolution metazoan tree of life. This week the article came out in Nature, and has been followed by a storm of really bad reporting:

Earth’s first animal was the ocean-drifting comb jelly, not the simple sponge, according to a new find that has shocked scientists who didn’t imagine the earliest critter could be so complex.

What’s wrong with this? Basically, the study showed that the line leading to the ctenophores may have diverged before the other metazoan lineages. Stating comb jellies were the “first animal” is going to lead to people thinking that all animals evolved from comb jellies! Some other stories on this article do specify the ctenophore lineage diverged first, which is somewhat less misleading. However, this lineage diverging first does not mean modern ctenophores were there at the time. We might also consider that at that divergence the other lineage produced led eventually to humans, and we certainly were not swimming about in the ocean with the ctenophores waiting for land-living plants and animals to evolve so we could get out and dry off. Modern humans are much different from their early ancestors, and modern ctenophores may be as well.

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This post was deleted after objections by the author of the paper discussed. Since these objections were not clarified, I have posted a heavily modified version of this post here.

Yes, the busy-ness has captured me. I am working on an entry right now about Triassic reptile trackways in Germany, but it’s going to take some time and I don’t want to screw it up by rushing. So I will try to get that to you tomorrow, and in the meantime you can stop by Catalogue of Organisms to read about aquatic sloths (!!), Tetrapod Zoology to read about crested porcupines, and test your knowledge of evolutionary relationships at Bayblab (discovered by way of Sandwalk).

I think the Bayblab quiz is a good example of some of the tendencies that we have that I mentioned in my entry on understanding evolutionary trees. Appearances can be deceptive–if we get tricked into thinking of evolution as a linear process rather than branching, we might classify some apparently simple creatures as distantly related that are actually just on the next branch over.

Like most new bloggers, I love collecting new links, and frequently check my Technorati authority rating. Unfortunately I find a significant number of the links I’m getting are from so-called “splogs”. These are spam blogs that link to various places in hopes of getting a trackback link which will increase the site’s page rank, or sometimes draw visitors to click on ads and generate revenue for the splogger. Splog entries are generated by bots that search for key words and link to blogs mentioning those. Understandably this complete lack of intelligent input leads to odd results.

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ResearchBlogging.orgTHE VERTEBRATE coagulation system is a complicated cascade of enzymes, yet it evolved by the gradual addition of enzymes. It is thought that this complex system evolved by the repeated duplication and divergence of two ancestral genes. We are most familiar with the prothrombin activators as essential clotting cascade elements, yet some snakes have weaponized these enzymes.

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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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THE PROPER practice of science requires adherence to the evidence above all, even when it leads us in directions we did not anticipate. While we would like to think that we succeed in this goal, perhaps sometimes scientific progress is slowed by dogmatic adherence to popular scientific models. Perhaps we would be better served by an “open science” model, setting aside such things as reams of gene sequences and fossil descriptions to see what others can come up with when their creativity is not straitjacketed by over-reliance upon the scientific method.

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ResearchBlogging.orgATTINE ANTS have been a theme at my blog recently. They first showed up in a discussion of their evolutionary tree, then in a post examining their relationship with the actinomycete bacteria that help protect their fungal gardens from parasites. In my reading I stumbled across the article that I will write about today, which seems to have discovered another part to the attine ant symbiosis. As of now this is the sole report on the occurrence of black yeasts living apparently parasitically on the attine ants, reliant upon the cuticular crypts that normally house helpful actinomycetes.

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