by Alok Jha
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A prosperous, happy society will need lots of intelligent people who treat each other with respect. They will look out for each other and come up with ever-better ways to improve their collective lot. Genes that contribute to health and intelligence are good things, and if natural selection was left to get on with it, these would be prevalent in society. Any “bad” genes for disease, disability or mental deficiency should be weeded out by the principles outlined by Charles Darwin in the 19th century. But medical technology has put a stop to this natural mechanism.
Even worse, the genes that contribute to the more preferable traits in society might themselves be at risk. If IQ is determined, to some extent, by genes, and people with high IQs do not have as many babies as those with lower IQ points, intelligence across the population will suffer. If being good to others is partly genetic, and good people are similarly less fecund than their bad cousins, then “badness” genes might be growing more popular.
“Currently it seems that there is a negative correlation in some places between intellectual achievement and fertility,” says Nick Bostrom, a philosopher and the head of the Future of Humanity Institute at the University of Oxford. “If such selection were to operate over a long period of time, we might evolve into a less brainy but more fertile species, Homo philoprogenitus (‘lover of many offspring’).”
Might “good” genes eventually be swamped by “bad” genes among humans?
We are all mutants
Steve Jones, a geneticist at University College London, thinks that our ability to cure diseases that would previously have killed us, the ways we move around the world, and our huge level of control over our bodies and our environments have all conspired to take power away from the natural forces of evolution.
Variations among humans are driven by genetic mutation. Every time a cell divides, the DNA within can mutate. Most changes have no overall effect and are never passed on to children. But rarely, the mutations can change the way some part of the body looks or works, and even more rarely, that change is fatal. As we age, the number of mutations adds up.
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Given that previously dangerous genetic mutations can now routinely survive and be passed on to children, what power is left for natural Selection in humans?
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The process by which a particular mutation becomes more common in a population is called selection. Within the past 5,000 years, for example, a gene for skin color mutated to give someone white as opposed to dark skin. The white skin, which has the advantage of being better at making vitamin D from sunlight, became useful for those living in northern Europe, where there was less sunlight. Selection pressure means that the white gene variant appears in 99 percent of Europeans, whereas 99 percent of Africans maintain the dark skin variant.
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Darwin expressed himself very gloomily on the future of humanity, on the ground that in our modern civilization natural selection had no play and the fittest did not survive.
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Mutation and selection are the raw materials for evolution, the stuff that the random forces of nature can shape into species. But where once a person’s genes had complete sway over their longevity, leaving only those with the “best” genes to survive and pass on their DNA, modern medicine and lifestyles have leveled the playing field, diminishing the stuff that evolution can play with. A lack of vitamin D does not need any genetic fixes today; it can be easily treated with food supplements. The genetic mutations we collect as we age might no longer kill us as we learn more about how to fix them. Where people in one part of the world might have been wiped out by a particular infection, medicine or a re-engineering of the local environment can save lives.
More important, given that previously dangerous genetic mutations can now routinely survive and be passed on to children, Jones questions what power is left for natural selection in humans.
The dysgenic dystopia
Dysgenics, the idea that bad genes are spreading in our population, was a term coined in the 1970s by the American physicist and Nobel laureate William Shockley. In the previous decades, he had developed a theory about a possible connection between race and intelligence. His argument, which used data from IQ tests on American soldiers, suggested that blacks were genetically inferior to whites and that intelligence in people who were mixed race depended on how much “white blood” they had in their ancestry. As a result, he called on people with low IQs to undergo voluntary sterilization, to stop them passing on their genes to a new generation of children.
The ideas are certainly dubious by today’s standards. But Shockley was not alone in thinking that undesirable genes could spread and compromise the progress of the human race—even the great naturalist Charles Darwin was not immune to pessimism about the fate of humans, according to Alfred Russel Wallace, the biologist and co-founder of the theory of natural selection. “In one of my last conversations with Darwin he expressed himself very gloomily on the future of humanity, on the ground that in our modern civilization natural selection had no play and the fittest did not survive,” wrote Wallace. “It is notorious that our population is more largely renewed in each generation from the lower than from the middle and upper classes.” The implication, of course, is that those in the lower classes were somehow biologically inferior, and that their children would be inferior too.
The early 20th century was marked by several attempts by scientists and governments to justify eugenics, a movement founded by Darwin’s half-cousin Francis Galton, and which tried to “improve” the human race by breeding out deleterious inherited traits, in everything from intelligence to temperament and morals.
“British eugenicists tended to look for ways to perpetuate the privileged classes, whereas American eugenicists tried to slow down the supposedly corrupting influence of the degenerate classes,” wrote biologists David Micklos and Elof Carlson in an article on the history of eugenics, published in Nature Reviews Genetics. “Eugenics researchers attempted to trace the inheritance of dysgenic traits through a family tree, and constructed pedigrees by interviewing living family members and by scrutinizing the records of poorhouses, prisons and insane asylums.”
In a precursor to some of Shockley’s ideas, the French aristocrat Joseph Arthur Gobineau proposed in the mid-19th century that the mixing of races was at the root of genetic deterioration. And eugenicists sometimes tried to provide a supposed scientific rationale for existing racial prejudice—in his influential book The Passing of the Great Race, Madison Grant warned that racial mixing was a social crime that would lead to the demise of white civilization.
German Nazi officials use calipers to measure an ethnic German’s nose. The Nazis developed a system of facial measurement that was supposedly a way of determining racial descent. The compiled results, based on biased samples, were used to back up the Nazi claim that Germans were a pure and superior “Aryan” race. Eugenicists would use similar details in a misguided attempt to encourage the spread of the “best” genes through society.
For American eugenicists, “feeble-mindedness” became an important idea around 1910. It was linked to abnormal behavior, promiscuity, criminality and social dependency. The influence of the eugenics lobby can be seen in the first sterilization law passed in Indiana in 1907, on the advice of prison physician Harry Clay Sharp. “Speaking at meetings of the American Medical Association, Sharp convinced fellow physicians to lobby their legislatures for laws to allow the involuntary sterilization of sex offenders, habitual criminals, epileptics, the ‘feebleminded’ and ‘hereditary defectives’,” say Micklos and Carlson. “The intent was to prevent alleged degenerates from breeding with each other or from contaminating ‘good genetic stock’ by reproducing with normal people.”
Marian Van Court, who runs an organization called Future Generations that tries to rehabilitate the image of eugenics, explains the potential dysgenic problem in terms of intelligence. “Since IQ is positively correlated to a number of desirable
traits (such as altruism, anti-authoritarian attitudes, and middle-class values of hard work, thrift, and sacrifice), when IQ declines, so do these traits,” she says. “People with low IQs are far more likely to become criminals, so the fact that our genetic potential for intelligence is declining means our genetic potential for crime is increasing. Moreover, some evidence suggests that despite lengthy sojourns in jail, criminals still manage to procreate at a faster rate than the rest of us.”
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There is fuzziness and dispute at the edges of the concept of disability. At what point does an illness become disabling?
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Van Court cites research by Richard Lynn of the University of Ulster to underline her point. He found that criminals in London had nearly twice as many offspring as noncriminals. “In demographic studies of fertility, the entire category of underclass males is frequently omitted because reliable data on their offspring simply can’t be obtained—their sexual behavior is often promiscuous, and their relationships transient,” she says. “Since twin studies and adoption studies have established that there is a substantial genetic component to criminality, the higher fertility of criminals significantly increases the genetic potential for criminality in the population.”
If you believe this description of society, criminality is on the rise and intelligence and good temperament are on the wane, at least genetically speaking.
Purposely choosing “undesirable” genes
Eugenics is not the only thing to note if you are thinking about the spread of so-called “undesirable” genes. Most people with normal hearing might consider deafness to be a terrible affliction that should be avoided or cured if possible. But many of those born deaf think of themselves as a cultural minority with shared customs and ways of living that should be preserved. “An analogy is drawn with members of minority ethnic communities, who share a common language,” says Tom Shakespeare, a bioethicist at the University of Newcastle. “Deaf people (who adopt a capital letter to signify this distinctiveness) share a culture based around sign language. Deaf people welcome the birth of Deaf children; they find the concept of prenatal testing for a deaf child deeply disturbing; they oppose the use of cochlear implants and other technologies to overcome this sensory loss or difference.” A minority of Deaf parents might one day go so far as to use genetic tests to make sure their children are born without hearing.
And how do you define “undesirable” anyway? Disability is something that we all assume we know about, but which is hard to actually define in practice. “There is fuzziness and dispute at the edges of the concept of disability,” says Jackie Scully, an ethicist at Newcastle University. “At what point, for example, does an illness become disabling, and how should we distinguish people who are disabled through chronic illness from those who have an impairment but are not ill? What about people who are phenotypically anomalous but reject the suggestion that they are disabled? Too easy recourse to the umbrella term of disability without really being clear what it covers also glosses over the fact that what we find undesirable about disability—its disadvantage, distress or pain—can arise for a number of distinct reasons, not all of them biological.”
Should we worry about dysgenics?
Undesirable genes that lead to deviations from what we might call “normal” may well spread. But thanks to genetic engineering and screening, so will the genes for desirable traits such as intellectual capacity, physical health and longevity, says Nick Bostrom. “In any case, the time-scale for human natural genetic evolution seems much too grand for such developments to have any significant effect before other developments will have made the issue moot.”
Organic Cell Disintegration
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In the center of each of our cells, stuck to the ends of the 46 strands of DNA that contain the instructions for building what we are, is a ticking clock. Every time a cell divides, this clock moves forward, each stroke bringing the cell closer to its eventual demise.
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This clock is the telomere, a strand of DNA that caps the end of the chromosomes. Each division shortens the length of a cell’s telomeres—very short telomeres lead to the death or disease of a cell, and this can cause a range of age-related diseases such as cancer, Alzheimer’s, heart attacks and strokes. Telomeres are crucial failsafes for cells, preventing them from growing out of control and becoming cancerous.
But Reinhard Stindl of the Institute of Medical Biology at the University of Vienna thinks that this natural erosion of telomeres might not be restricted to individual cells. He thinks it might also be occurring in every successive generation of humans, and that this could lead to a point where the human population will crash. “Over thousands of generations the telomere gets eroded down to its critical level. Once at the critical level we would expect to see outbreaks of age-related diseases occurring earlier in life and finally a population crash. Telomere erosion could explain the disappearance of a seemingly successful species, such as Neanderthal man, with no need for external factors such as climate change.”
Not just humans, either. Stindl believes that across all species, apart from bacteria and algae, telomeres are getting shorter with every generation. That means that an inbuilt evolutionary clock is ticking down to an inexorable extinction date for all complex life.
What is a telomere?
Deep in the nuclei of our cells lie 23 pairs of gossamer-like strands of DNA. The chromosomes, one of each pair coming from mum and the other from dad, contain genes that code for proteins spaced out by vast stretches of DNA that used to be called “junk” but are now referred to simply as “non-coding.” At the end of each chromosome is the telomere, a characteristic sequence of base-pairs present in everything from the simplest amoeba to humans, which acts as a full stop to the long strand of DNA.
Telomeres are there to protect the chromosomes, which might otherwise fuse in the nucleus or swap genetic material by accident. These sorts of mistakes can lead to cancer or other abnormal behavior by the cell.
The end caps are also crucial in ensuring that cells can divide properly, and therefore in keeping a life form healthy. Every time a cell divides, its machinery has to copy all the base-pairs of DNA exactly, so that each daughter cell contains the full complement of genetic material. Unfortunately, this copying machinery can never get down to the ends of the DNA strands. If the telomeres were not there, the copying mechanism would snip off the ends of chromosomes every time they did their work. This would lead to the loss of crucial DNA (and its genetic information) every time a cell divided. Instead of snipping off crucial genes, then, the cell division process snips off a section of telomere.
Artist’s impression of the two sex chromosomes, X and Y. The DNA is coiled tightly inside these structures, which are capped with telomeres and sit inside the nucleus of every cell.
The length of a telomere is a sign of the age of a cell. As cells divide or carry out their functions, they pick up mutations and errors in their DNA. These errors are all potentially dangerous; any of them could lead to cancer. When telomeres are short, it means that a cell is old and, at this stage, probably contains lots of DNA errors that have built up over time. Further divisions are prevented, as they would be potentially risky for the health of the organism as a whole. The cell enters a phase known as senescence and can divide no more.
Telomeres through the generations
Mass extinctions on Earth are well documented and, if not fully explained, there are plenty of ideas about how or why they might have occurred, including major environmental changes or asteroid impacts. For more than a century, though, scientists have been puzzled by the slower background rate of extinction of many of the species that have disappeared through the history of life on Earth. Well over 99 percent of species that have ever existed are now no longer around, but only around four percent of the loss can be explained by mass extinctions. Most species are not killed by asteroids or climate change; they just seem to whimper out.
The fossil record also shows that species go through fits and starts of change, rather than the gradual and continuous pace of evolution that might be expected from Charles Darwin’s theory of natural selection. There are long periods in history where evolution just seems to stagnate.
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SINCE LIFE BEGAN
Over 99% species have disappeared
Only 4% due to mass extinctions
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Reinhard Stindl thinks he has the answer to both these conundrums. He believes that species have remained happily stable throughout the history of the Earth until a point where they have suffered a surprise population crash, caused by drastically short telomeres.
He discussed his idea in a 2004 paper for the Journal of Experimental Zoology Part B: Molecular and Developmental Evolution. “The species clock hypothesis,” he wrote, “is based on the idea of a tiny loss of mean telomere length per generation. This mechanism would not rapidly endanger the survival of a particular species. Yet, after many thousands of generations, critically short telomeres could lead to the weakening and even the extinction of old species and would simultaneously create the unstable chromosomal environment that might result in the origination of new species.”