Here is an excellent article on the biology of sexual orientation. We all know this is a contentious issue — are we born with an orientation, or is it a ‘choice’ that people make? — and the article just lays the facts out for us and points out some of the lacunae in our knowledge.
Two new Homo fossils are described in this week’s Nature, and here they are.
Some two-bit publicity hound can die, and that’s all you can find on any of the television channels … a whole grand species can go extinct, and there’s almost nothing.
Say goodbye to the Yangtze River dolphin. It is officially extinct. The funeral will be poorly attended, and it will be forgotten, except in a few academic papers.
Since I was asked what a cnidarian “head” is in reference to this work on multi-headed cnidarians, I’ll answer. In short, they don’t have one.
It’s a collision! Two great carnivals on the same day. Check out Carnival of the Spineless #23 from sodden Great Britain, where the molluscs are thriving, and also read Tangled Bank #85, the Reductionist’s Tale at Migrations.
This is a short video clip of myotome formation in a zebrafish embryo — it’s the subject of an upcoming column in Seed, so I’m putting a short visual aid here.
You can Download the Quicktime movie (620K), or you can watch it via YouTube. Watch closely, it’s short and it flies by!
People are always arguing about whether primitive apes could have evolved into men, but that one seems obvious to me: of course they did! The resemblances are simply too close, so that questioning it always seems silly. One interesting and more difficult question is how oysters could be related to squid; one’s a flat, sessile blob with a hard shell, and the other is a jet-propelled active predator with eyes and tentacles. Any family resemblance is almost completely lost in their long and divergent evolutionary history (although I do notice some unity of flavor among the various molluscs, which makes me wonder if gustatory sampling hasn’t received its proper due as a biochemical assay in evaluating phylogeny.)
One way to puzzle out anatomical relationships and make phylogenetic inferences is to study the embryology of the animals. Early development is often fairly well conserved, and the various parts and organization are simpler; I would argue that what’s important in the evolution of complex organisms anyway is the process of multicellular assembly, and it’s the rules of construction that we have to determine to identify pathways of change. Now a recent paper by Shigeno et al. traces the development of Nautilus and works out how the body plan is established, and the evolutionary pattern becomes apparent.
A little knowledge would short circuit a lot of strange speculation. That picture to the right is of a shark caught in Malaysia, and people are calling those odd dangly bits “legs”. Despite the fact that someone said what they actually are in a comment early on, there are people arguing both that a shark with legs is evidence for evolution, and that it is evidence for creation.
They’re both wrong.
It’s a male shark. Those are the shark’s claspers, or intromittent organs. The shark does the usual act you’d expect with a female of the species, and like many shark species, it has clasper spurs, or little poky bits that help lock the organ into the female’s cloaca while he gets happy.
They aren’t homologous to legs at all. We also wouldn’t expect to find legs on a shark — they aren’t in the lineage that led to tetrapods.
I’m actually most surprised that a worker at the Malaysian Fisheries Development Board, who found this animal, didn’t recognize that these were just ordinary claspers. Anyone who has worked with sharks for even a little while would know about these structures. I suspect someone at the board is pulling the media’s, and the public’s, leg.
You know you want to see this: here’s a photo of two sharks getting affectionate. Shark lovin’ often involves a fair amount of biting and tearing, and leaves scars that you can find in captured specimens, so I don’t recommend trying this at home. Especially since sharks don’t believe in safewords.
