stoutfellow

Researchers have discovered an animal without mitochondria.

(It's a parasite whose life cycle does not require aerobic metabolism, so it dumped it.)

"It's a strange strange world we live in, Master Jack."

Apparently, sometime in the not-too-distant future, a white dwarf star is going to swallow its normal-star partner. The resulting nova will be the brightest on record - brighter than Sirius, possibly even outshining Venus.

The event is predicted to occur in 2083 +/- 15 years. It's unlikely I'll live to see it, but some of you might.

Here's the story.

A quote from The CryptoNaturalist's Twitter feed:

"Birds are dinosaurs who shrugged off a couple apocalypses. Some eat bone marrow. Some drink nectar. They outswim fish in the sea. They smile politely at gravity’s demands.
I am grateful to see them. I am grateful to feed them. I am grateful to know them."

One of the books I'm currently reading is Michael Collins' _Carrying the Fire_, an autobiographical work on his career as a pilot and astronaut. It's not badly written, a good mix of human interest and technical detail.

The passage I just read told of the beginning of the Apollo 11 flight, including a description of the Command Module as the three of them climbed in. He spent a couple of pages on Velcro: what it is, how it works, and what it's good for. Of course, this was written in the early '70s, before the stuff became so widely used; it just struck me as interesting that he felt the need to explain this.

This is fascinating: a fossil bed which seems to have been laid down within an hour of the Chicxulub impact - a Cretaceous Pompeii. (H/t to Christine Forber.)

The Great Unconformity is a paleontological mystery: there is a stratigraphic boundary where the rocks below are much, much older than the rocks above. An explanation has been proposed: it's the result of worldwide erosion by glaciers during one of the Snowball Earth episodes. It may also explain the apparent suddenness of the Cambrian Explosion, when the number and diversity of life forms on Earth rose sharply.

I remember Isaac Asimov, in one of his 1960s science columns, proposing that it was the result of massive tides from the much-nearer Moon, but that has the disadvantage of not explaining the suddenness of the transition. Still, it seems that he was in the vicinity of a better answer.

About a month ago, I posted a bit of speculation, stemming from David Reich's Who We Are and How We Got Here, in connection with the expansion of the Yamnaya people into Europe five thousand years ago.

In the introduction, Reich makes it clear that the field of ancient DNA studies is in rapid flux, and that any claims in the book are subject to change.

Well, the very item that I talked about has been voided; plague hit Europe before the Yamnaya got there.

This is going to be rather long and geeky, I'm afraid.

I'm currently reading Who We Are and How We Got Here, by David Reich. It's about discoveries, over the last twenty years or so, concerning the DNA of past populations of humans around the world. It's a fascinating book, and I may give it a review later on, but the chapter I just completed triggered a series of thoughts.

About 5000 years ago, a population originating in the East European steppe, the Yamnaya culture, expanded hugely into Europe, displacing a resident farming population. Part of their success can be attributed to the discovery of the wheel; charioteers made a formidable fighting force against a sedentary, wheel-less population, But there may have been a second factor. Analysis of the teeth of the indigenous farmers, before the Yamnaya expansion, shows no indication of exposure to Yersinia pestis - the plague bacterium - but afterward, both populations show traces of its presence. It is entirely possible that the farmers were decimated by plague, easing the way for the intruders.

What follows is my own reasoning, not Reich's, and if anyone wants to rebut, I'll be glad to read it.

A digression: for a long time, the received wisdom was that disease pathogens undergo evolutionary pressure towards reduced virulence - a host who survives for a long time after infection is more likely to infect others. A generation or so ago, Paul Ewald pointed out that this applies only to diseases spread by personal contact, not to vector-borne diseases; for those, a host does not need to be out and about to spread the disease. (His Evolution of Infectious Disease is also fascinating.)

The reason this comes to mind is this: the Yersinia DNA recovered from the farmer and Yamnaya populations lacks the genes that permit transmission by fleas. The plague outbreak (if such it was) was pneumonic plague - which is directly transmitted, not vector-borne. At that time, then, plague would have been subject to pressure towards reduced virulence, which would allow for mutual adaptation, given enough time, between the Yamnaya and the pathogen, while the farming population would have faced a virgin-field epidemic, rather like the Native Americans at the time of the Columbian Exchange.

Most of the genome of modern Europeans is derived from the Yamnaya; there is relatively little trace of the ancient farmers.

This is very cool: moths have developed spoofing techniques to confuse bats.

There is a lineage of salamanders characterized by the following.
1) They're all female.
2) To produce offspring, each female must mate with (male) salamanders of three different species and incorporate some of each male's genes into their eggs.

Here's the scoop.

Haldane scores again.