Discussion On Whether Biological Evolution Of The Human Has Stopped
In this paper, my aim is to discuss the argument put forward by Professor Steve Jones FRS, Emeritus Professor of Human Genetics at UCL, that the biological evolution of the human may have stopped as well as to discuss alternative theories discussed by scientists which offer alternative conclusions. due to fewer gene mutations and a human population that is spread out, Darwin’s theory of natural selection (defined by Darwin as ‘descent with modification’) is slowing down and, in many ways, has stopped. Or has it? Naturalist and broadcaster, Sir David Attenborough, upholds Jones’ view albeit with a different rationale. He says “Our evolution is now cultural. We can inherit a knowledge of computers or television, electronics, airplanes, and so on. ” Attenborough holds the view that humans learn from other humans in a variety of ways and that, over time, systems of behaviour and knowledge are transmitted culturally across human populations.
Biologically speaking, what is happening to ensure the continued evolution and existence of the human? Is it the simplistic argument that once human lineage developed a sophisticated enough culture and a large enough brain that humans ceased evolving? Or is it that with the advent of agricultural development around 10,000 years ago that biological evolution began to be supplanted by a cultural evolution? Many evolutionary psychologists and biologists accept neither of these factors and many, including Professor Jones, have reached the opposite conclusion. There are significant medical factors to consider in our continued evolution. The development of modern medicine is one more example of biological evolution being supplanted by cultural evolution. Those proponents of the argument that humans have stopped evolving advocate that it is no longer natural selection (defined by Darwin as ‘descent with modification) that allows us to adapt in order to build resistance to disease. Rather, they advocate that humans have culturally adapted to disease through the advancement of antibiotics and vaccines. Therefore, given this scenario, the common diseases that we, as humans, are susceptible to such as heart disease and cancer, have arisen from our early biological adaptations to a hunter-gatherer foraging environment and that these adaptations have continued because the evolution of the human has stopped. Indeed, anthropologist George J Armelagos (Paleopathelogy At the Origins of Agriculture 1984) argued that human health, in fact, declined with the development of modern agricultural practices because the human body is hard-wired to function in a Stone Age environment rather than the high tech environment of medical advancement we know today. This has led to an increase in infectious and nutrition-related diseases in humans regardless of what crops they grow or in which area they live.
In order to understand our evolution at a biological level, we must also understand cultural evolution and discuss how do we define cultural evolution of the human as opposed to the cultural evolution of animals? Mark Nielsen. (Imitation, pretend play, and childhood: Essential elements in the evolution of human culture? Journal of Comparative Psychology, Vol 126(2), May 2012, 170-181) suggests that perhaps the period of childhood in the human has played a part in the cultural development of the mind with their features of play and imitation. In imitating adults, children will copy random actions and gestures such as replicating the way a household item or toy is used. These behaviours lead the way to the transmission of cultural ideas across each generation because, as they play together, children put together rules and interpretations. Task-relevant actions are created and transmitted across the generations. Those tasks which comprise irrelevant actions and gestures are gradually filtered from the behavioural repertoire of the human. These culturally transmitted patterns of behaviour, therefore, are designed to become more efficient over time. It is from play that the building blocks of the reality of human cultural and behavioural practices begins. Nielsen further suggests that this type of play and imitation represent the foundation of the development of human culture and, most importantly, that neither (play and imitation) are seen in animals. (https://psycnet. apa. org/record/2011-18196-001)
Then there is the wider issue of how culture overlaps with biological evolution in the shaping of our species. The cultural nature of the human mind (eg. the development of cognitive processes such as language and emotion) is rooted in human biology: it has been attributed to social learning mechanisms which are unique to the human population. Culture also influences biology as our cognitive capacities have adapted to work in conjunction with human cultural evolution (Sperber 1996). https://royalsocietypublishing. org/doi/full/10. 1098/rstb. 2008. 0147(Boyd & Richerson 1985; Whiten 2005; Mesoudi et al. 2006b).
Furthermore, culture provides a second inheritance system for human behaviour. The appearance of design in human behaviour therefore has at least two possible causes, biological or cultural evolution, and explaining the origins of complex and adaptive human behaviours requires us to understand which inheritance systems carry and shape which behaviours, as well as understanding how these two inheritance systems interact. English anthropologist Sir Francis Galton (1822 - 1911) contributed his controversial theories on human biological evolution in his book Hereditary Genius (1869). This was a scientific and social attempt to study genius and greatness. Galton, who was half cousin to Charles Darwin and who had read Darwin’s On the Origin of Species, explaining the development of animal and plant species, which he sought to apply to humans. Galton believed that the future for the human was gloomy and that those people of “low quality” i. e. of lower intellect, were having more children than those of “high quality” i. e. of higher intellect. He, termed his theory ‘eugenics’ in 1883, as he proposed that the best human qualities were primarily inherited through genes, therefore creating geniuses, regardless of living conditions or education which saw the origination of the theory of nature vs nurture. Galton, along with others including George Bernard-Shaw,(1856-1950) playwright and political activist and Marie Stopes (1880-1958) author and campaigner for women’s rights, firmly believed that it was their duty to guarantee the biological future of the human population by ensuring that people of good quality reproduced and that those of poor quality did not. As is evidenced over the last one hundred years, this theory led to disasters, such as the holocaust, and posed huge ethical and racial questions.
Darwin strongly disagreed with Galton’s theory as his theory of natural selection allowed for variations and mutations in gene transmission, an idea that was already being used by science fiction writers with their creations of giant rodents and aliens. However, in the 1940s, there was a belief within the genetics and physics communities that the human race was going to endure a significant increase in the rate of mutation through the use of radiation. This became a reality with the development of the hydrogen bomb which was dropped on Japanese cities, Nagasaki and Hiroshima in August 1945. Although this was done for military reasons, the scientific community had a significant involvement and were sure that they would see an increased rate in gene mutation in the offspring of the Japanese who survived.
The results of the exhaustive long-term scientific experiments to assess genetic mutations were surprising. The scientists analysed thousands of millions of blood proteins from children of parents who had been irradiated and survived and those that had not been irradiated. They found only 28 mutations. However, these mutations manifested equally in the children of parents who had been irradiated and those whose parents had not been irradiated, therefore demonstrating that they could find no effect at all of the bombs. More interestingly, as discussed by Professor Jones in a presentation in February 2015, 26 of the 28 mutations were in the father and not the mother.
This unexpected result demonstrates another factor in our biological evolution, which is the process of aging which occurs primarily from damage to our DNA which often manifests itself in age-related diseases such as some cancers which are a genetic disease of the cells which decay and degenerate with age which are continually divided and subdivided which allows for ‘mistakes’ i. e. gene mutations. A male is going to create more mutations due to the fact that throughout his life he is creating sperm allowing for a greater chance of mutation when passed on in his DNA, whereas a the finite number of reproductive eggs of the female are created and effectively ‘frozen’ before she leaves the womb herself. The eggs then mature and are released during the course of her reproductive life. This is known as meiosis. Therefore, offering a much lower chance of mutation in the DNA from the mother.
Consequently, there are a number of health conditions such as achondroplasia, which manifests as reduced bone growth such as that characterised by dwarfism, which are the result of gene mutations which are passed on by older males. The multiplication of this mutated gene would be between 15 to 20 times that of a young male. This is corroborated by Michael Eisenberg, Associate Professor of Urology at the Stanford Medical Centre, who wrote that there is an 'increased risk of autism, psychiatric illness, neurologic disease. . . and chromosomal abnormalities in children born to older fathers,” (Association of paternal age with perinatal outcomes between 2007 and 2016 in the United States: population based cohort study. BMJ (Clinical research ed. )Khandwala, Y. S. , Baker, V. L. , Shaw, G. M. , Stevenson, D. K. , Lu, Y. , Eisenberg, M. L. )
However, contrary to the view of Professor Jones, Eisenberg goes on to state that “Twice as many dads of newborns are now in the 40-plus age group, compared to the 1970s. Of the roughly 4 million births each year in the U. S. , about 9 percent of fathers are over 40. And about 40,000 newborns have a father over the age of 50,” According to the Office for National Statistics in the UK (https://www. ons. gov. uk/peoplepopulationandcommunity/birthsdeathsandmarriages/livebirths/bulletins/birthsbyparentscharacteristicsinenglandandwales/2016), the average age of all fathers of live-born children in England and Wales was in 2016 33. 3 years, which was up from 32. 9 years in 2014. Given the above studies, it appears that as the average age of fatherhood is increasing, there follows an increased chance for gene mutation thus perpetuating Darwin’s Theory of Evolution. However, Professor Jones, qualifies his statement by concluding that “it is really old fathers that matter, and the number of really old fathers has definitely gone down”. He adds “in the developed world now, there are fewer older fathers than there might have been a century or more ago …in Dickensian times fathers started getting down to their paternal duties when they were 16 or so, which they probably did because the chances of staying alive were not all that great”. We should also remember up until 1960 there was no contraception allowing for the possibility of children born to younger parents.
Jones further argues that in the developed world parents start to reproduce early and finish reproducing early which suggests that rather than an increase in the rate of mutation, there is actually a decrease. In the past, the average human lifespan was much shorter. For example, in the seventeenth century only 33% out of every million births survived to age 21. However, by the twentieth century we see a survival rate of over 90%. This not only results in a lower percentage of older breeding males, thus reducing the transmission of genes associated with age-related disease, it has other significant implications supporting the argument for continuing human evolution. A recent study Humans co-evolved with immune-related diseases -- and it's still happening (Nov 2019) carried out by researchers at the Radboud Institute for Molecular Life Science in the Netherlands suggests that the shorter human lifespan did not allow for the development of diseases that we now know develop later in life such as inflammatory and autoimmune diseases. The study suggests that human evolution continues to occur in the field of immune related diseases and our body’s ability to fight them. According to Jorge Dominguez-Andres, a postdoctoral researcher at Radboud ,the fact that we now have longer lifespans means that we are seeing the consequences of infections that our ancestors had to combat. The study suggests that some of the gene mutations that allow humans to fight potentially fatal infections also serve to make us more prone to some inflammatory and autoimmune diseases.
The researchers advocate that our ancient genetic origins mean that people of African or Eurasian descent may develop immune-related diseases. Senior author of the study, Mihai Netea, evolutionary biologist and immunologist at Radbout University shares evidence that the human immune system is still evolving through the mutations that create inflammation - the body’s most efficient defence against infectious disease. Netea compiled data from immunology, genetics, virology and microbiology studies to identify how human DNA was altered from humans from different communities infected with viral or bacterial diseases. This alteration, or mutation, subsequently produced inflammation. However, while these mutations protected these communities against certain diseases, they were also associated with the appearance of new inflammatory conditions such as Lupus and Crohn’s disease. According to study authors Dominguez-Andres and Netea 'There seems to be a balance. Humans evolve to build defenses against diseases, but we are not able to stop disease from happening, so the benefit we obtain on one hand also makes us more sensitive to new diseases on the other hand,' says Dominguez-Andres. 'Today, we are suffering or benefiting from defenses built into our DNA by our ancestors' immune systems fighting off infections or growing accustomed to new lifestyles. ”
In their 2009 book The 10,000 Year Explosion: How Civilization Accelerated Human Evolution, Gregory Cochran and Henry Harpending https://www. researchgate. net/publication/230796728_Why_genes_still_matter_A_review_of_Gregory_Cochran_and_Henry_Harpending_The_10000_Year_Explosion_How_Civilization_Accelerated_Human_Evolution contend that cultural evolution and genetic evolution are not mutually exclusive and that they actually feed off each other in an “…endless dance of biological and cultural change”. They suggest that, rather than there having been no biological change in humans over the past 50,000 years, that in fact the evolution of the human as quickened over the last 10,000 years. For example, they attribute the success of the Indo-European population to the rapid natural selection of a single gene allowing lactose tolerance, which gave them a nutritional advantage over the majority of other populations such as the Native Australians, Chinese, Native South Americans, Native South Africans and Japanese who have not inherited the gene.
Cochran and Harpending further hypothesize that the psychological differences that have enabled humans to problem solve and to develop their market economies and agriculture are the result of natural selection. They calculate that evolution is currently occurring at about “100 times faster than its long-term average over the 6 million years of our existence”. Population bottlenecks caused through changes in climate, earthquakes, volcanos and even genocide, have occurred over millennia. These, in turn, have lead to a major reduction in population size with implications for human evolution due to genetic drift. The end result was a dramatic reduction in genetic diversity. However, since the advent of air travel bringing cultural diversity the world is much more open and available, thus spreading the gene pool. Professor Jones concludes “We are moving into an era of unprecedented openness and large population size… so I can summarise. . that evolution has lost its power: there are fewer mutations, there is much less natural selection, and there is effectively no population bottlenecks, so the Darwin machine has come, in some senses, to a stop. ” In summary, whilst Professor Jones puts forward a strong argument for the evolution of the human to have stopped such as population bottlenecks and reduced genetic diversity, these are outweighed by contemporary studies, outlined above, conducted by Jorge Dominguez-Andres and Mihai Netea of Radbout University and by Cochran and Harpending.
