Tag: science

Screening for Stroke

There has been no cost-effective way to screen for strokes, which cost the US government 10s of billions of $ a year. That could be about to change, thanks to a breakthrough technology from CVR Medical. What 3D seismic imagery did for super quick discoveries in the oil and gas industry, CVR’s sensory system could do for the medical industry.

Settlement of the Americas

24 ka Americans?

About 24 ka ago, when much of North America was buried under the ice of the Last Glacial Maximum, a few hunters took shelter in a small cave above the Bluefish River in what is now northwestern Yukon. The hunters had killed a Yukon horse and were butchering it using super-sharp stone shards called microblades. As they sliced out the horse’s meaty tongue, the microblades left distinctive cuts in its jaw bone. Millennia later, archaeologist and doctoral candidate Lauriane Bourgeon spotted those marks through her microscope at the University of Montreal and added the fragment of ancient jaw bone to her small selection of samples for radiocarbon dating.

2017-04-26: 130 ka Americans? Those are fighting words, 6x-10x earlier than generally believed. Needs a LOT more evidence.

An unidentified Homo species used stone tools to crack apart mastodon bones, teeth and tusks approximately 130 ka ago at a site near what’s now San Diego.

2021-11-13: There’s plenty of evidence that North America was settled early, but not successfully:

The problem with the idea of an early, pre-Amerindian settlement of the Americas is that ( by hypothesis, and some evidence ) it succeeded, but ( from known evidence) it just barely succeeded, at best. Think like an epidemiologist – once humans managed to past the ice, they must have had a growth factor greater than 1.0 per generation – but it seems that it can’t have been a lot larger than that, because if they had averaged, say, 3 surviving kids per generation ( r = 1.5) , their population would have exploded, filling up all the habitable territories south of the glaciers in less than 2 ka. Maybe they didn’t have atlatls. The Amerindians certainly did. Maybe they arrived as fishermen and didn’t have many hunting skills. Those could have been developed, but not instantaneously. An analogy: early Amerindians visited some West Coast islands and must have had boats. But after they crossed the continent and reached the Gulf of Mexico, they had lost that technology and took several 1000 years to re-develop it and settle the Caribbean. Along this line, coastal fishing settlements back near the Glacial Maximum would all be under water today. Maybe they fought among themselves to an unusual degree. I don’t really believe in this, am just throwing out notions. Maybe their technology and skills set only worked in a limited set of situations, so that they could only successfully colonize certain niches. Neanderthals, for example, don’t seem to have flourished in plains, but instead in hilly country. On the other hand, we don’t tend to think of modern human having such limitations. One can imagine some kind of infectious disease that made large areas uninhabitable. With the low human population density, most likely a zoonosis, perhaps carried by some component of the megafauna – which would also explain why it disappeared.

2022-02-08: A more detailed look at the 24 ka hypothesis

I present this history of the last 36 ka of migration from the perspective of a scientist who places genetic evidence in the forefront of the investigation and then tests the models it produces with archaeological, linguistic, and environmental evidence. Around 36 ka BP, a small group of people living in East Asia began to break off from the larger ancestral populations in the region. 25 ka BP, the smaller group in East Asia itself split into 2. 1 gave rise to a group referred to by geneticists as the ancient Paleo-Siberians, who stayed in Northeast Asia. The other became ancestral to Indigenous peoples in the Americas.

24 ka BP, both groups independently began interacting with an entirely different group of people: the ancient Northern Siberians. Some archaeologists and geneticists argue that this meeting of the 2 grandparent populations of Native Americans—the group in East Asia and the ancient community in Northern Siberia—occurred because people moved north, not south, in response to the last glacial maximum (LGM), a period in which much of northern North America was covered by massive glaciers. Thus, many geneticists look north, to Beringia, for the location of the refugia that may have allowed the ancestors of Native Americans to survive the ice age.



2022-08-14: 37 ka evidence

About 37ka BP, a mother mammoth and her calf met their end at the hands of human beings.

Bones from the butchering site record how humans shaped pieces of their long bones into disposable blades to break down their carcasses, and rendered their fat over a fire. But a key detail sets this site apart from others from this era. It’s in New Mexico – a place where most archaeological evidence does not place humans until 10s of 1000s of years later. Based on genetic evidence from Indigenous populations in South and Central America and artifacts from other archaeological sites, some scientists have proposed that North America had at least 2 founding populations: the Clovis and a pre-Clovis society with a different genetic lineage.

Extended evolutionary synthesis

EES argues that while the existing framework of evolutionary theory, known as the “modern synthesis,” is basically solid, it needs to be expanded to account for newly recognized drivers of evolution. One such driver is epigenetics — gene-expression changes that stem from exposure to, say, pesticides. While these epigenetic changes are not encoded in an organism’s genes, they do give rise to physical and behavioral differences that natural selection can act upon. We now have a better picture of the regulatory process on genes. Epigenetics changes the landscape in genetics because it’s not only the pure DNA sequence which influences what’s going on at the level of proteins and enzymes. There’s this whole other stuff, the other 95 percent of the genome, that acts like rheostats — you slide this thing up and down, you get more or less of this protein. It’s a critical thing in how much of this protein is going to be made. It’s interesting to think about the way in which cultural phenomena, which we used to think were things by themselves, can have this effect on how much messenger RNA is made, and therefore on many aspects of gene regulation.

State

In physics, math, and computer science, the state of a system is an encapsulation of all the information you’d ever need to predict what it will do, or at least its probabilities to do one thing versus another, in response to any possible prodding of it. In a sense, then, the state is a system’s “hidden reality,” which determines its behavior beneath surface appearances. But in another sense, there’s nothing hidden about a state—for any part of the state that never mattered for observations could be sliced off with Occam’s Razor, to yield a simpler and better description.

When put that way, the notion of “state” seems obvious. So then why did Einstein, Turing, and others struggle for years with the notion, along the way to some of humankind’s hardest-won intellectual triumphs?

Leapfrogging Moore’s Law

fun idea: save compute power by selectively using lower precision math, then reinvest the savings:

We run the algorithm in double precision to a given error bound and measure energy consumption. This is our energy budget. We next run the algorithm in single precision for a number of iterations, followed by double precision for a number of iterations, consuming the same energy as before, and measure the error bound. The ratio between the first error bound and the second is the achieved improvement factor. For Laplace, we were able to achieve an improvement factor of 10^4, for Rosenbrock,10^8

Wycheproof

In cryptography, subtle mistakes can have catastrophic consequences, and mistakes in open source cryptographic software libraries repeat too often and remain undiscovered for too long. Good implementation guidelines, however, are hard to come by: understanding how to implement cryptography securely requires digesting decades’ worth of academic literature. We recognize that software engineers fix and prevent bugs with unit testing, and we found that many cryptographic issues can be resolved by the same means. These observations have prompted us to develop Project Wycheproof, a collection of unit tests that detect known weaknesses or check for expected behaviors of some cryptographic algorithm. Our cryptographers have surveyed the literature and implemented most known attacks. As a result, Project Wycheproof provides tests for most cryptographic algorithms, including RSA, elliptic curve crypto, and authenticated encryption.