A Bit More Detail

Assorted Personal Notations, Essays, and Other Jottings

Posts Tagged ‘human beings

[LINK] On a possible replacement of Europe’s ancient population of homo sapiens

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The Dragon’s Tales linked to the Cell paper “Pleistocene Mitochondrial Genomes Suggest a Single Major Dispersal of Non-Africans and a Late Glacial Population Turnover in Europe”. The abstract is eye-catching.

How modern humans dispersed into Eurasia and Australasia, including the number of separate expansions and their timings, is highly debated. Two categories of models are proposed for the dispersal of non-Africans: (1) single dispersal, i.e., a single major diffusion of modern humans across Eurasia and Australasia; and (2) multiple dispersal, i.e., additional earlier population expansions that may have contributed to the genetic diversity of some present-day humans outside of Africa. Many variants of these models focus largely on Asia and Australasia, neglecting human dispersal into Europe, thus explaining only a subset of the entire colonization process outside of Africa. The genetic diversity of the first modern humans who spread into Europe during the Late Pleistocene and the impact of subsequent climatic events on their demography are largely unknown. Here we analyze 55 complete human mitochondrial genomes (mtDNAs) of hunter-gatherers spanning ∼35,000 years of European prehistory. We unexpectedly find mtDNA lineage M in individuals prior to the Last Glacial Maximum (LGM). This lineage is absent in contemporary Europeans, although it is found at high frequency in modern Asians, Australasians, and Native Americans. Dating the most recent common ancestor of each of the modern non-African mtDNA clades reveals their single, late, and rapid dispersal less than 55,000 years ago. Demographic modeling not only indicates an LGM genetic bottleneck, but also provides surprising evidence of a major population turnover in Europe around 14,500 years ago during the Late Glacial, a period of climatic instability at the end of the Pleistocene.

Written by Randy McDonald

February 8, 2016 at 8:08 pm

[LINK] “DNA from Neandertal relative may shake up human family tree”

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I came across very recently Ann Gibbons’ September 2015 Sciencemag article noting yet another remarkable turn in the history of the hominid family.

In a remarkable technical feat, researchers have sequenced DNA from fossils in Spain that are about 300,000 to 400,000 years old and have found an ancestor—or close relative—of Neandertals. The nuclear DNA, which is the oldest ever sequenced from a member of the human family, may push back the date for the origins of the distinct ancestors of Neandertals and modern humans, according to a presentation here yesterday at the fifth annual meeting of the European Society for the study of human evolution.

Ever since researchers first discovered thousands of bones and teeth from 28 individuals in the mid-1990s from Sima de los Huesos (“pit of bones”), a cave in the Atapuerca Mountains of Spain, they had noted that the fossils looked a lot like primitive Neandertals. The Sima people, who lived before Neandertals, were thought to have emerged in Europe. Yet their teeth, jaws, and large nasal cavities were among the traits that closely resembled those of Neandertals, according to a team led by paleontologist Juan-Luis Arsuaga of the Complutense University of Madrid. As a result, his team classified the fossils as members of Homo heidelbergensis, a species that lived about 600,000 to 250,000 years ago in Europe, Africa, and Asia. Many researchers have thought H. heidelbergensis gave rise to Neandertals and perhaps also to our species, H. sapiens, in the past 400,000 years or so.

But in 2013, the Sima fossils’ identity suddenly became complicated when a study of the maternally inherited mitochondrial DNA (mtDNA) from one of the bones revealed that it did not resemble that of a Neandertal. Instead, it more closely matched the mtDNA of a Denisovan, an elusive type of extinct human discovered when its DNA was sequenced from a finger bone from Denisova Cave in Siberia. That finding was puzzling, prompting researchers to speculate that perhaps the Sima fossils had interbred with very early Denisovans or that the “Denisovan” mtDNA was the signature of an even more ancient hominin lineage, such as H. erectus. At the time, researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who had obtained the mtDNA announced that they would try to sequence the nuclear DNA of the fossils to solve the mystery.

After 2 years of intense effort, paleogeneticist Matthias Meyer of the Max Planck Institute for Evolutionary Anthropology has finally sequenced enough nuclear DNA from fossils of a tooth and a leg bone from the pit to solve the mystery. The task was especially challenging because the ancient DNA was degraded to short fragments, made up of as few as 25 to 40 single nucleotides. (Nucleotides—also known as base pairs—are the building blocks of DNA.) Although he and his colleagues did not sequence the entire genomes of the fossils, Meyer reported at the meeting that they did get 1 million to 2 million base pairs of ancient nuclear DNA.

They scanned this DNA for unique markers found only in Neandertals or Denisovans or modern humans, and found that the two Sima fossils shared far more alleles—different nucleotides at the same address in the genome—with Neandertals than Denisovans or modern humans. “Indeed, the Sima de los Huesos specimens are early Neandertals or related to early Neandertals,” suggesting that the split of Denisovans and Neandertals should be moved back in time, Meyer reported at the meeting.

Researchers at the meeting were impressed by this new breakthrough in ancient DNA research. “This has been the next frontier with ancient DNA,” says evolutionary biologist Greger Larson of the University of Oxford in the United Kingdom.

Written by Randy McDonald

February 8, 2016 at 8:04 pm

[LINK] “The first Indo-French Prehistorical Mission in Siwaliks and the discovery of anthropic activities”

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The Dragon’s Tales linked to a remarkable paper that claims to have found stone tools 2.6 million years old in India.

This paper presents the first Indo-French Prehistorical Mission in the Himalayan foothills, northwestern India, and introduces the results of the multidisciplinary research program “Siwaliks” under the patronage of Professor Yves Coppens, from the Collège de France and Académie des Sciences, France. This program is dedicated to the discovery of cut marks on mineralized bovid bones collected among vertebrate fossils in a fluviatile formation named “Quranwala zone” in the Chandigarh anticline, near the village Masol, and located just below the Gauss–Matuyama polarity reversal (2.58 Ma). Artefacts (simple choppers, flakes) have been collected in and on the colluviums. This important discovery questions the origins of the hominins which made the marks.

As I understand it, this is very early.

Written by Randy McDonald

February 1, 2016 at 1:22 pm

[BLOG] Some Monday links

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  • Discover‘s Body Horrors notes éléphants can transmit tuberculosis to humans.
  • Crooked Timber shares a photo of a street of San Francisco.
  • The Dragon’s Tales links to a study suggesting impacts by comets and asteroids could not have eroded Mars’ atmosphere.
  • Marginal Revolution notes a study suggesting ethnic groups with a long history of agriculture fare better in modern capitalism.
  • Strange Maps depicts shifting patterns of male names in France from the Second World War on.
  • Window on Eurasia notes what I think is the fundamental unacceptability of the Minsk accords for Ukraine and describes the history of the Nogays, a Turkic group of the North Caucasus.

[LINK] “Your paper brain and your Kindle brain aren’t the same thing”

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Public Radio International hosts an article noting that people read online and printed materials differently. E-books and books are not perfectly interchangeable after all.

Manoush Zomorodi, managing editor and host of WNYC’s New Tech City, recalls a conversation with the Washington Post’s Mike Rosenwald, who’s researched the effects of reading on a screen. “He found, like I did, that when he sat down to read a book his brain was jumping around on the page. He was skimming and he couldn’t just settle down. He was treating a book like he was treating his Twitter feed,” she says.

Neuroscience, in fact, has revealed that humans use different parts of the brain when reading from a piece of paper or from a screen. So the more you read on screens, the more your mind shifts towards “non-linear” reading — a practice that involves things like skimming a screen or having your eyes dart around a web page.

“They call it a ‘bi-literate’ brain,” Zoromodi says. “The problem is that many of us have adapted to reading online just too well. And if you don’t use the deep reading part of your brain, you lose the deep reading part of your brain.”

So what’s deep reading? It’s the concentrated kind we do when we want to “immerse ourselves in a novel or read a mortgage document,” Zoromodi says. And that uses the kind of long-established linear reading you don’t typically do on a computer. “Dense text that we really want to understand requires deep reading, and on the internet we don’t do that.”

Written by Randy McDonald

January 28, 2016 at 5:11 pm

[LINK] “Can Animals Think Abstractly?”

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Barbara King’s NPR commentary is unsettling, mainly for its implications about humans. Are we really actually fully conscious?

In her January Scientific American piece titled “What Animals Know about Where Babies Come From,” anthropologist Holly Dunsworth makes a convincing case that despite popular assumptions to the contrary, animals generally — and our closest living relatives, the great apes, specifically — don’t understand that sexual intercourse produces babies.

Dunsworth leads off with an example (something I also wrote about here at 13.7) in which the captive gorilla Koko, who knows some American Sign Language and comprehends some spoken English, is asked to make choices among several options presented verbally and in diagram form related to “family planning.” Dunsworth dismisses the suggestion that Koko is cognitively equipped to understand the four different scenarios by which she could potentially become a mother — and I couldn’t agree more.

I also think Dunsworth is spot on when she argues that “reproductive consciousness” is unique to our own species. But outside the realm of strange anthropomorphic assumptions made by caretakers of media-star apes, do people really go around thinking that wild animals, farm animals or their dog and cat companions grasp where babies come from? I don’t know of evidence one way or the other.

People do often assume that animals’ behavioral choices are highly cognitive and strategic when they may simply be products of natural selection — and this is part of Dunsworth’s main point. When a gorilla silverback male, for example, takes over a new group of females and offspring from a resident rival male, he may commit infanticide; at the point when a female’s young baby dies, lactation hormones no longer suppress ovulation and she comes back into estrus, thus becoming a likely mate for the conquering male.

“We love to narrate observations of animal sex and parenting with language that implies common ground between them and us,” Dunsworth writes. But, “animals may carry out all kinds of seemingly complex behaviors without actually anticipating the outcomes.”

Written by Randy McDonald

January 20, 2016 at 1:14 pm

[OBSCURA] Changing world population balances, 1800 to 2100

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The Russian Demographics Blog was the most recent source to link to Max Galka’s remarkable map showing changing populations in the recent past and the projected future.

For thousands of years, Asia has been the population center of the world. But that’s about to change.

Asia contains 7 of the 10 most populous countries in the world, the two largest of which, China and India, each individually have larger populations than Africa, Europe, or the Americas. And as I’ve demonstrated previously, the eye-popping population density in regions such as Tokyo and Bangladesh is an order of magnitude greater than anywhere in the western world.

Two hundred years ago, the figures were even more extreme. In 1800, nearly two thirds of the world lived in Asia. And at that time China had a larger population than Africa, Europe, and the Americas combined.

Asia dominates the world population landscape, and it has for at least the last two and a half thousand years. [. . . T]he relative population sizes of Asia, Africa, and Europe have remained surprisingly constant for thousands of years. Since at least 400 BC, 60% or more of the world has lived in Asia.

According to the U.N. Population Division, the population of Africa is poised to explode during the next 85 years, quadrupling in size by 2100.

The U.N. attributes this change to two factors: Africa’s high fertility rates (African women have on average 4.7 children vs. a global average of 2.5) and its young population, many of whom will be reaching adulthood in the coming years and having children of their own.

Written by Randy McDonald

January 18, 2016 at 6:54 am


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