Researchers Find Evidence That Human Evolution Is Still Actively Happening
Scientists discover that humans are still evolving, with natural selection weeding out certain diseases.
A large new study says humans are still evolving. Scientists found that natural selection is weeding out harmful genetic mutations from our gene pool.
While we tend to think of evolution as laborious process that takes a long period of time, there also changes that can take place over one or two generations. Researchers from Columbia University analyzed DNA from 210,000 people in the United States and Britain and found that certain genetic variants, particularly those linked to Alzheimer’s disease and heavy smoking appear less frequently in people who live longer. This suggests that such genes are being less favored and may be on the way out of the human genome.
The scientists considered 8 million common mutations to arrive at those which seem to get less widespread with age. Other genetic variations that the scientists think are being pushed out by natural selection include predispositions towards heart disease, high cholesterol, asthma and obesity. These appear less often in those who live longer, indicating that genes with fewer such illnesses are the ones more likely to get passed down.
Hakhamanesh Mostafav, an evolutionary biologist at Columbia University who led the study, explained that people who carry harmful genetic variants die more frequently, making these mutations appear more rarely in the older portion of the populace.
“If a genetic variant influences survival, its frequency should change with the age of the surviving individuals,” said Mostafav.
Why is this evidence of evolution at work? Mostafav says that considering the large sample of the study, finding only two mutations with less prevalence is what indicates that they are being “weeded out”. His colleague, the study’s coauthor Joseph Pickrell, an evolutionary geneticist at Columbia and New York Genome Center, called their findings a “signal” that supports evolutionary theory.
"It's a subtle signal, but we find genetic evidence that natural selection is happening in modern human populations," said Pickrell.
Specifically, the researchers saw a decrease in the frequency of the ApoE4 gene linked to Alzheimer’s disease in women over 70. A similar decrease was observed in the frequency of the mutated CHRNA3 gene, linked to heavy smoking in men.
"It may be that men who don't carry these harmful mutations can have more children, or that men and women who live longer can help with their grandchildren, improving their chance of survival," elaborated the study’s coauthor Molly Przeworski, an evolutionary biologist at Columbia University.
Interestingly, the scientists also found that those who were predisposed to delayed puberty and child-bearing had longer lives, indicating that fertility-related variants are continuing to evolve as well. The environment might have an influence on that trend, they suggest.
"The environment is constantly changing," said the study's lead author, said Mostafavi. "A trait associated with a longer lifespan in one population today may no longer be helpful several generations from now or even in other modern day populations."
Check out the study here, published in PLOS Biology.
- The meaning of the word 'confidence' seems obvious. But it's not the same as self-esteem.
- Confidence isn't just a feeling on your inside. It comes from taking action in the world.
- Join Big Think Edge today and learn how to achieve more confidence when and where it really matters.
If you're lacking confidence and feel like you could benefit from an ego boost, try writing your life story.
In truth, so much of what happens to us in life is random – we are pawns at the mercy of Lady Luck. To take ownership of our experiences and exert a feeling of control over our future, we tell stories about ourselves that weave meaning and continuity into our personal identity.
Researchers hope the technology will further our understanding of the brain, but lawmakers may not be ready for the ethical challenges.
- Researchers at the Yale School of Medicine successfully restored some functions to pig brains that had been dead for hours.
- They hope the technology will advance our understanding of the brain, potentially developing new treatments for debilitating diseases and disorders.
- The research raises many ethical questions and puts to the test our current understanding of death.
The image of an undead brain coming back to live again is the stuff of science fiction. Not just any science fiction, specifically B-grade sci fi. What instantly springs to mind is the black-and-white horrors of films like Fiend Without a Face. Bad acting. Plastic monstrosities. Visible strings. And a spinal cord that, for some reason, is also a tentacle?
But like any good science fiction, it's only a matter of time before some manner of it seeps into our reality. This week's Nature published the findings of researchers who managed to restore function to pigs' brains that were clinically dead. At least, what we once thought of as dead.
What's dead may never die, it seems
The researchers did not hail from House Greyjoy — "What is dead may never die" — but came largely from the Yale School of Medicine. They connected 32 pig brains to a system called BrainEx. BrainEx is an artificial perfusion system — that is, a system that takes over the functions normally regulated by the organ. The pigs had been killed four hours earlier at a U.S. Department of Agriculture slaughterhouse; their brains completely removed from the skulls.
BrainEx pumped an experiment solution into the brain that essentially mimic blood flow. It brought oxygen and nutrients to the tissues, giving brain cells the resources to begin many normal functions. The cells began consuming and metabolizing sugars. The brains' immune systems kicked in. Neuron samples could carry an electrical signal. Some brain cells even responded to drugs.
The researchers have managed to keep some brains alive for up to 36 hours, and currently do not know if BrainEx can have sustained the brains longer. "It is conceivable we are just preventing the inevitable, and the brain won't be able to recover," said Nenad Sestan, Yale neuroscientist and the lead researcher.
As a control, other brains received either a fake solution or no solution at all. None revived brain activity and deteriorated as normal.
The researchers hope the technology can enhance our ability to study the brain and its cellular functions. One of the main avenues of such studies would be brain disorders and diseases. This could point the way to developing new of treatments for the likes of brain injuries, Alzheimer's, Huntington's, and neurodegenerative conditions.
"This is an extraordinary and very promising breakthrough for neuroscience. It immediately offers a much better model for studying the human brain, which is extraordinarily important, given the vast amount of human suffering from diseases of the mind [and] brain," Nita Farahany, the bioethicists at the Duke University School of Law who wrote the study's commentary, told National Geographic.
An ethical gray matter
Before anyone gets an Island of Dr. Moreau vibe, it's worth noting that the brains did not approach neural activity anywhere near consciousness.
The BrainEx solution contained chemicals that prevented neurons from firing. To be extra cautious, the researchers also monitored the brains for any such activity and were prepared to administer an anesthetic should they have seen signs of consciousness.
Even so, the research signals a massive debate to come regarding medical ethics and our definition of death.
Most countries define death, clinically speaking, as the irreversible loss of brain or circulatory function. This definition was already at odds with some folk- and value-centric understandings, but where do we go if it becomes possible to reverse clinical death with artificial perfusion?
"This is wild," Jonathan Moreno, a bioethicist at the University of Pennsylvania, told the New York Times. "If ever there was an issue that merited big public deliberation on the ethics of science and medicine, this is one."
One possible consequence involves organ donations. Some European countries require emergency responders to use a process that preserves organs when they cannot resuscitate a person. They continue to pump blood throughout the body, but use a "thoracic aortic occlusion balloon" to prevent that blood from reaching the brain.
The system is already controversial because it raises concerns about what caused the patient's death. But what happens when brain death becomes readily reversible? Stuart Younger, a bioethicist at Case Western Reserve University, told Nature that if BrainEx were to become widely available, it could shrink the pool of eligible donors.
"There's a potential conflict here between the interests of potential donors — who might not even be donors — and people who are waiting for organs," he said.
It will be a while before such experiments go anywhere near human subjects. A more immediate ethical question relates to how such experiments harm animal subjects.
Ethical review boards evaluate research protocols and can reject any that causes undue pain, suffering, or distress. Since dead animals feel no pain, suffer no trauma, they are typically approved as subjects. But how do such boards make a judgement regarding the suffering of a "cellularly active" brain? The distress of a partially alive brain?
The dilemma is unprecedented.
Setting new boundaries
Another science fiction story that comes to mind when discussing this story is, of course, Frankenstein. As Farahany told National Geographic: "It is definitely has [sic] a good science-fiction element to it, and it is restoring cellular function where we previously thought impossible. But to have Frankenstein, you need some degree of consciousness, some 'there' there. [The researchers] did not recover any form of consciousness in this study, and it is still unclear if we ever could. But we are one step closer to that possibility."
She's right. The researchers undertook their research for the betterment of humanity, and we may one day reap some unimaginable medical benefits from it. The ethical questions, however, remain as unsettling as the stories they remind us of.
- Prejudice is typically perpetrated against 'the other', i.e. a group outside our own.
- But ageism is prejudice against ourselves — at least, the people we will (hopefully!) become.
- Different generations needs to cooperate now more than ever to solve global problems.
SMARTER FASTER trademarks owned by The Big Think, Inc. All rights reserved.