[This is actually the second part of the post, see "Background information"]
[Note: the Dead Sea has low UV radiation, as probably did the Mediterranean during the MSC, and likely Lake Assal, due to low topography and relative thick ozone, reducing natural selection for very dark melanized skin, hair and eyes.]
The Tubercular Hominid | The Loom | Discover Magazine
At Djibouti, scientists found a surprising diversity of Mycobacterium bacteria that cause tuberculosis. Many scientists have wondered how long these bacteria have been attacking the lungs of our ancestors. Hippocrates described cases that appear to be tuberculosis, and ancient mummies show signs of the disease. For earlier chapters in the evolution of TB, scientists have begun to turn to the bacteria’s DNA. "The first studies pointed to a relatively recent origin of the disease... they estimated that a single successful ancestor gave rise to all current strains about 20,000 to 35,000 years ago". "But French researchers have found that people in Djibouti carry strains of TB that are significantly different than anything seen before. They have many more genetic differences than have been found in human TB strains from anywhere else in the world. Yet they are more closely related to other human TB than to the Mycobacterium species that infect cattle and other animals. The scientists then turned the mutations of the Djibouti strains into a molecular clock. They estimate that the ancestor of today’s human TB existed some three million years".
In the 1940s, researchers proposed that the three tapeworm species that infect humans descend from ancestors which pioneered our guts when cattle and pigs were first domesticated some 10,000 years ago. But a close look at their DNA showed otherwise. Scientists found that the closest relatives of human tapeworms did not make relatives of cows or pigs their intermediate hosts. Instead, they lived inside East African herbivores such as antelopes, and made he lions and hyenas that kill them their final hosts. The researchers then looked at the amount of variation between the DNA from different species of tapeworms. According to the agricultural hypothesis, that variation should have pointed to a common ancestor 10,000 years ago. But the scientists concluded that this common ancestor could have lived as long as a million years ago.
The scientists proposed that tapeworms began adapting to our hominid ancestors when they began putting more [Note: uncooked] meat in their diet. By scavenging or hunting on the East African savannas, our ancestors became an attractive new habitat for the tapeworms, and new species evolved that were specialized only to live inside us. Only hundreds of thousands of years later did they make cows and pigs their intermediate hosts.
Given TB’s similar antiquity, I wonder if it may have made a similar leap. Many closely relatives to Mycobacterium tuberculosis live in bovids–cows and their relatives–which hominids might have encountered as they began to scavenge meat. Could a sick wildebeest have been our patient zero?
Still, the question remains: why is so much TB diversity hiding out in Djibouti, while one branch seems to have exploded about 30,000 years ago and spread around the world, such that today it makes up the vast majority of TB cases? The paper’s authors hazard that this lineage spread out of Africa with the migration of humans to other parts of the world. That makes sense up to a point. The bacteria that cause ulcers, Helicobacter pylori, spread this way–so faithfully in fact that it acts as a marker for human migrations to different parts of the world. But the new TB 30,000 years ago was able to spread much more aggressively than the other strains, which apparently are still restricted to the region where they’ve been for millions of years. It’s hard to understand what sort of social or ecological change could have created the conditions that would favor such a superior bug".
(30ka - more advanced boats, bundled rafts? no more daily dive foraging due to fishing/netting/harpooning? Oldest twisted/dyed flax fibers 34ka, Oldest spinning 28ka, 24ka fishing camp at Sea of Galilee)
Malaria For Brains | The Loom | Discover Magazine
One of the most important groups of receptors that Plasmodium (malaria parasite) needs to latch onto are sugars known as sialic acids, which are found on all mammal cells. These sugars play a crucial but mysterious role in human evolution. As I’ve written here (and here), almost all mammals carry a form of the sugar called Neu5Ac on their cells, as well as a modified version of it, known as Neu5Gc. They argue that a change in the receptors on the cells of hominids was the key. Ironically, this same change of receptors may have also allowed our ancestors to evolve big brains. Malaria may simply be the price we pay for our gray matter. The scientists argue that some seven million years ago the common ancestor of chimpanzees and humans carried both kinds of sugars on their cells. This ancient ape would sometimes get sick with malaria, caused by the common ancestor of today’s P. rechnowi and P. falciparum. This ancient parasite preferred to latch onto Neu5Gc to get into its host’s blood cells. Hominids then branched off from other apes, walking upright and moving out of the jungle into open woodlands. They still got sick with the old malaria, because they still produced both kinds of sugars. But then, about three million years ago, our ancestors lost the ability to make Neu5Gc. Initially this was a great relief, because the malaria parasites had a much harder time gaining entry into our cells. [Chimps at in- wet-/woodland/savannah, Humans at coast/highland]
But this relief did not last, the scientists argue. Sometimes mutant parasites emerged that did a better job of latching onto the one sugar hominids still made, Neu5Ac. They now could get into hominid red blood cells, while other Plasmodium parasites were still making do with the other apes. Over time these parasites evolved a better ability to infect hominids.
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Brain energy crisis starts in womb, continues in youth: human have 60% smaller GI, 60% larger brain.
Solving the Brain
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Human verbal grooming (tele-grooming)
Analysis of a sample of human conversations shows that about 60% of time is spent gossiping about relationships and personal experiences (dive - click hum, backfloat = chat but no fur grooming, scalp hair grooming).
Co-evolution of neocortex size, group size and language in humans
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The results support the hypothesis that brain size evolution in primates was associated with visual specialization. The present study reports a test of the hypothesis that increased reliance on binocular mechanisms underlies the expansion of visual brain areas and overall brain size. [Note: humans have both good binocular color vision (expected for daylight fruit forager) and good light/dark adaptation accommodation (not expected unless diver), can see clearly underwater, see Moken children.]
Binocularity and brain evolution in primates ? PNAS
