Neanderthal and Denisovan Genes – and Covid-19

The media reported last week that genes from Neanderthals protect many of us against severe Covid-19. Those genes actually come from Denisovans too: another early human species. Unfortunately, a different set of Neanderthal genes increases our chances of serious Covid. This post goes behind the news and looks at our connection to these two prehistoric creatures, as well as their genes’ impact on Covid risk. It also looks at those genes’ frequency among modern ethnic groups.

Neanderthal woman
Neanderthal woman (from the Neanderthal Museum)

Neanderthals and Denisovans

Denisovan girl
Denisovan girl (by Maayan Visuals)

We’ve known about Neanderthals since the 1860s, and archeologists have found hundreds of their fossils and tools. Denisovans, however, were only identified in 2010. Much about them remains unclear, and we only have a handful of fossils. But we know they had bigger molars than Neanderthals or Homo sapiens — more like earlier members of the Homo genus. We also know Denisovans shared the Neanderthals’ massive build, flat noses, protruding jaws and brow-ridges, sloping foreheads, and flat and long heads. Those oddly shaped Neanderthal heads contained brains bigger than ours, so Denisovans may have had bigger brains too. We don’t know whether that means these other species were smarter.

Fortunately, we have both species’ DNA, extracted from the fossils.

Classification and Hybrids

The Neanderthals and Denisovans are classified Homo neanderthalensis and, tentatively, Homo denisova. They evolved in Eurasia from a shared ancestor called Homo heidelbergensis. We’re their smaller, weaker African cousins. Our species probably descends from Homo heidelbergensis too, but the Homo sapiens branch of the tree diverged earlier. Still, we were close enough to cross-breed and produce fertile offspring.

Members of different species usually can’t do that: they can’t produce fertile offspring. Horses and donkeys can’t, even though they’re closely related — members of the Equus genus. Cross-breeding them produces sterile mules (and hinnies). The same goes for lions and tigers, members of the Panthera genus, which produce sterile hybrids called ligers and tigons. So we must have been very closely related to Neanderthals and Denisovans — closer than horses and donkeys or lions and tigers. It’s not unprecedented. Wolves and coyotes can produce fertile offspring. So can cows and buffalo, as well as servals and housecats, which have been bred to produce a beautiful spotted pet called a Savannah cat. In each case, some of the hybrid offspring may be sterile, particularly among the males. But enough can reproduce to pass on hybrid genes.

Neanderthal, Denisovan, sapiens family tree
The convoluted Homo genus family tree. The vertical axis measures time in millions of years past.

Prehistoric Encounters and Modern Ethnic Groups

We met Neanderthals and Denisovans when our species spread out from Africa into Eurasia, around 60,000 years ago. So their genes occur among Europeans and Asians. They’re also found among Native Americans, Australian Aboriginals, North Africans, and all other peoples who migrated through Eurasia before reaching their long-term homes. Europeans and mainland Asians average something like 2% Neanderthal, while Australian Aboriginals, Polynesians, and Indonesians range from 1% to 6% Denisovan. And many in those populations have some of both.

Only Sub-Saharan Africans lack significant Neanderthal or Denisovan genes. That’s because their ancestors did not migrate through Eurasia. Prehistoric Africans may have interbred with non-sapiens too, but those would’ve been African species, so far unidentified.

Of course, members of every ethnic group usually have some ancestors from another group. So as they say with medicines, individual results may vary.

The Hybrids’ Helpful Haplotypes

Last month, scientists announced a haplotype — a cluster of genes — that helps destroy RNA viruses, including Covid-19. Each copy of the haplotype reduces the odds of severe Covid by 22%. That haplotype occurs in Neanderthals and Denisovans but not in early Homo sapiens. Our species got it from the other two species — from cross-breeding.

DNA is rarely simple, however, and neither is immunity. Scientists have also identified a Neanderthal haplotype that increases the risk of severe Covid-19. Those genes double our chances of hospitalization. They don’t seem to come from Denisovans.

Today’s Ethnic Groups and Natural Selection

The currently helpful haplotype appears in about 50% of non-Africans. That’s a lot for genes from Neanderthals and Denisovans, since each represents such a small share of our genetic inheritance. So that haplotype probably protected us against Covid-like viruses in the past, leading to heavy selection for those genes. In fact, the haplotype’s frequency apparently surged during just the past thousand years (in addition to earlier increases). That suggests we faced a Covid-like disease recently: during the Middle Ages (the Postclassical period) or later.

The currently harmful Neanderthal haplotype appears in about 65% of Southeast Asians and 16% of Europeans. It’s mostly absent from East Asians and of course from Africans. That haplotype probably protected against diseases faced by Southeast Asians in the past and so grew more common there. But its vulnerability to Covid-like diseases led to selection against those genes in other regions.


Images:

© 2021 by David W. Tollen. All rights reserved.

History Tells Us Congress CAN Impeach the President After His Term

The Constitution says nothing specific about whether Congress can impeach an official after his or her term. That didn’t stop the House of Representatives from impeaching the Secretary of War in 1876, after he left office — or the Senate from trying him. And history tells us Congress got it right that year, just as they apparently will again in 2021. The Framers based the impeachment process on the English Parliament’s power to impeach. And English impeachments could start after the official left office. In fact, Parliament impeached an official named Warren Hastings in 1787 and tried him between 1788 and 1795 — though he left office in 1784. The Hastings impeachment battle raged while the Framers wrote the Constitution, and it played a central role in their thinking.

The House of Commons, where they impeached Hastings
The House of Commons, Late 1700s

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History Tells Us the President Cannot “Self-Pardon”

The Framers of the Constitution based the presidential pardon on the English monarch’s power to grant pardons. And the monarch could not pardon himself — could not use executive power to escape the judgement of the courts. Parliament established that principle during the century before the Constitutional Convention, when it tried and executed King Charles I. To the Framers, then, “pardon” meant legal forgiveness granted to another. The authority they gave the President does not include a “self-pardon.”

even with 3 positions, Charles I could not self-pardon
Charles I, triple portrait by Anthony van Dyck

The Constitution does not address a “self-pardon,” and caselaw offers little guidance on whether the President has such a power. But the history of the Seventeenth Century does.
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What Really Happens in a Challenged Election

by David W. Tollen and guest contributor Robert W. Tollen

Many commentators assume the new House of Representatives would choose the President after a challenged election — with each state’s delegation casting a single vote. Others say the Supreme Court would decide. Each scenario gives Republicans an advantage, since they’ll probably control more state delegations, despite their overall minority in the House, and they appointed most of the Justices. But in fact, neither scenario is likely, and the commentators focused on them misunderstand the law. State governments resolve disputes about their voters’ presidential electors, under state law. And the new Congress rules on challenges to those decisions in the normal way, with each house voting by simple majority.

The Unlikely Case of a Tie or Plurality in the Electoral College

When does the House of Representatives choose the President, voting by state? Only when no candidate gets a majority of the electors, per the rules in the Twelfth Amendment.

The electors tied in 1824, so the House decided.
In 1824, the House chose the President because, with three major candidates, no one had earned a majority of electors. That had never happened and hasn’t since.

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America Has No Guarantee of Freedom

In a second term, the ballot box would no longer restrict Trump. So we can expect:

  • Expanded use of the Department of Justice (DoJ) against the President’s opponents, including members of Congress.
  • More use of force against protesters.
  • Federal tolerance of crime against the President’s opponents (e.g., Michigan’s governor).
  • Refusal of federal disaster funds and other resources for blue states.
  • Further suppression of information on Covid-19’s nationwide impact.
  • Prompt firing of senior officials and federal prosecutors who try to restrain the President.
  • White House orders blocking DoJ prosecution of the President’s allies.
  • More separation of children from immigrant parents.
  • Withdrawal of federal resources aimed at curbing White supremacists.
  • Federal support for attacks on the voting process, particularly in swing states, probably leading to “disqualification” of large numbers of ballots and voters in 2022 and 2024.

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King George III: The Abdication that Never Happened

George III was Britain’s king during the American Revolution. The Declaration of Independence called him, “A Prince whose character is … marked by every act which may define a Tyrant.” But recent research has revealed a surprise about the king — one that hardly smacks of tyranny. In 1783, as the Revolutionary War drew to a close, George III almost abdicated—as revealed by a draft abdication speech in his own hand, recently discovered. The king’s speech blames the loss of the colonies on selfish partisanship within Britain. (Apparently, little has changed in the U.K. or in its former colonies.) King George also concluded that he had nothing left to offer. “A long Experience … has gradually prepared My mind to expect the time when I should be no longer of Utility to this Empire; that hour is now come; I am therefore resolved to resign My Crown and all the Dominions appertaining to it to the Prince of Wales my Eldest Son and Lawful Successor and to retire to the care of My Electoral Dominions the Original Patrimony of my Ancestors.” (The last point means he planned to move to his family’s duchy in Germany.) Continue reading “King George III: The Abdication that Never Happened”

Police History: Constable vs. Paramilitary

Calls to abolish or massively reform America’s police sound new and radical. Yet history offers a very old model for those reforms: an alternative to our current military style of policing. In the world of the Founding Fathers, civilian constables enforced the law. They had done so for 150 years in the American colonies — and for longer in England. And they would continue well into the 19th Century.

police history: a constable or beadle
An English constable (technically, a beadle)

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This Week in History: Althing

This week in 930 CE, the chieftains of Iceland established the Althing, which remains the country’s parliament. It’s the world’s oldest surviving legislature. Northmen (sometimes called Vikings) had arrived on the island about 60 years before, and now they set about to govern themselves – meeting outdoors at a place called Thingvellir, which means “assembly fields,” near modern-day Reykjavik.

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