Archaic hominins, namely Neanderthals and Denisovans, are assumed to have interbred with modern humans according to many popular theories. Numerous hypotheses are currently being tested to prove such theories proposed by geneticists, archaeologists, anthropologists and others of the science community. Research has found that interspecies breeding with these early humans may have added many profound benefits for these hybrid humans survival, but also gives rise to the possible susceptibility to common viral infections, allergies and diseases. These genetic components that exist inside many modern humans are called innate immunity genes. These genes are the body’s first defense mechanism and take part in the development of the human immune system. With this in mind, the popular media article that I have chosen, by author Sarah Kaplan, references Matthieu Deschamps’s scientific article. It showcases what makes up the genes within modern humans and why it might be reasonable to assume that the Neanderthals and Denisovans are the ones partly to blame for our genetic makeup.
Before addressing Sarah Kaplan’s portrayal of the information presented by Matthieu Deschamps, it is necessary to review how innate immunity has evolved and how these archaic hominins came to interbreed with modern humans. To highlight these essential details, Deschamps conducts a genome-wide study to provide an overview of how innate immunity genes were chosen in the process of evolutionary selection. According to Deschamps’s scientific article, it states that, “Importantly, unlike adaptive immunity whose parameter variation is mostly somatic and presents limited heritability, variation of innate immunity is germline encoded and thus needs to be best-adapted to ensure host survival” (Deschamps, 2016: 6). These earlier humans may have remained in smaller populations in specific areas within Europe and East Asia, thus allowing them to adapt to their respective environments, and gain some form of innate immunity that would help them survive. In addition to local adaptation, innate immunity was also brought about with the introduction of pathogens that immensely affected selective pressures on host genomes to increase the rate of survival. Deschamps presents several steps which were taken to analyze the various gene sets relating humans innate immunity to Neanderthals and Denisovans. Some of these investigative procedures were to look at what selective types and constraints, throughout the evolutionary process of innate immunity, induced the increase in variability for the purpose of adapting to certain environments. As well as calculating the time period when numerous interspecies breeding occurred between early and modern humans to provide an estimation for when genetic adaptation began to take place. Utilizing the widely renown 1000 Genome Project, as well as public databases, such as Gene Ontology and InnateDB—some of the genes did not appear in gene data sets when filters were in place—the primary findings of this article found that under strong selective constraints innate immunity genes, that are germ line encoded, evolve while harmful mutations are removed. Purifying selection allows genes to evolve to deal with the immune deficiencies, while positive selection, under strong constraints, has been shown to sway towards situational adaptations. Through admixture, modern humans with Neanderthal or Denisovan ancestry may have inherited or created advantageous variation to improve adaptive capabilities regardless of the situation. As for the age estimation for when the majority of interbreeding between modern humans and early humans occurred, this was estimated to be between 6,000 and 13,000 years, as around this time the population of humans were moving away from hunting and gathering towards agriculture. With the introduction of farming, the need for food becomes much greater due to the increasing population of modern humans that have geographically spread out since migrating out of Africa. Also, the necessity of cattle including exposure to hazardous waste had brought about within modern humans, to a certain extent, new genetic alterations when confronted by viruses. The study concludes that, although Neanderthals and Denisovans may have contributed greatly to the adaptive ability of innate immunity genes that modern humans have inherited, these archaic hominins do not have certain alleles considering their rarity. This conclusion is warranted by the fact that these alleles are also ancestral to modern humans, meaning that they are not emphasized genetically as much in modern humans genomes. Even though concrete results have been presented to support Deschamps hypothesis regarding innate immunity, these archaic humans may not be the direct origin of adaptive variation in the evolution of innate immunity. One future experiment stated in Deschamps article was, “test whether the Neandertal-introgressed variation detected at this gene cluster has any functional impact on TLR-mediated immunity to infection” (Deschamps, 2016: 18). This is an essential experiment because toll-like immune receptors detects certain molecular patterns that works to suppress viruses from accumulating. While observing what the effects of early hominins gene variation does to the recognition pattern, will give more insight to how the immune systems has evolved overtime. Another question that definitely should be addressed would be, how are genetic variability rates of immune systems in modern humans different from all known early hominin relatives?
Now that the scientific article has been analyzed, we will proceed to interpret Kaplan’s understanding of the information. Sarah Kaplan’s article had portrayed some useful information that solidified her interpretation of the scientific article. Although, she neglected to point out that Deschamps’s was not concluding that their primary findings were completely accurate and that there were still more unknown factors that could provide insight into this issue. Aspects of the scientific article that is represented in Kaplan’s article include Neanderthal and Denisovan genetics in modern humans and a few details regarding innate immunity’s advantages and disadvantages. According to Sarah Kaplan’s article, “Got allergies? Blame the Neanderthals”, she states “if you’ve ever battled an infection, you have your distant Neanderthal relatives to thank. But if you wrestle with allergies, that’s their fault too” (Kaplan, 2016). With the current acquired knowledge of our distant hominin relatives, it is very difficult to deny such a statement considering the evidence of innate immunity lingering within humans. On the other hand, it may be too early to assume that modern humans only interbred with Neanderthals and Denisovans. There is not much known about other hominins that could have come into contact with modern humans. Kaplan brings about another response stating,”Since the superior immune system was an evolutionary advantage, those traits would have spread quickly throughout the modern human population” (Kaplan, 2016). Since modern humans migrated out of Africa hundreds of thousands of years ago, mostly due to changes in the desert climate, assimilating amongst the early hominins across a wide geographic range would definitely support Kaplan’s assumption. The accuracy of Kaplan’s statements is adequate in relaying points discussed in Deschamps’s scientific article. For example, Kaplan’s article emphasizes that Neanderthals and Denisovans had already been regionally spread out around Europe and Asia, which makes it very plausible to assume that these early humans were already exposed to certain types of pathogens. Prior exposure to such environment-based pathogens becomes embedded within the immunity-related genes of Neanderthals and Denisovans. This allows the immune system to create counter measures against the effects of the pathogens that had once affected these small populations, but not longer pose a threat. Just as modern humans innate immunity has evolved under certain selective pressures, constraints, and environmental factors, the same scenario can also apply to these early human relatives. On the other hand, Kaplan did not provide insight regarding the level of influence selective pressures has on innate immunity genes in controlling mutations, which were stated in the scientific article. Rather, Kaplan states certain points such as the purpose of innate immunity and how it functions, how the inherited immune system is more robust in defending against foreign germs as a result of interspecies breeding, and modern human populations drove the Neanderthals and Denisovans to extinction. Considering that only a certain percentage of these ancestral DNA lingers within modern humans, it is difficult to assume that certain mutations, that occurred throughout evolution, may not have passed on due to speciation, regional adaptations, or even dietary changes. Without mentioning these specific factors which influenced the evolution of innate immunity, the purpose of relaying accurate information is defeated. Therefore, creates a fractured idea of interspecies breeding and how modern humans acquired such an immune system. Another vital piece of information that Kaplan overlooks in her article is that, the scientific article concludes that innate immunity may not have been a direct result of interspecies breeding between these early humans and modern humans. Deschamps’s article notes that specific alleles are very rare in Neanderthals, Denisovans and modern humans that would solidify the connection that innate immunity was a direct inheritance from these early human relatives. For the purpose of discussing these new findings in a very brief manner, this popular media article performs adequately. Several minute details mentioned in the scientific article are very important, but are not abundantly noted in Kaplan’s article making her conclusions about the primary findings misleading to the reader. As for how I would present the research article to the general public, my approach would consist of defining the main goal of this research article and presenting its primary findings alongside brief evolutionary explanations. As well as deliver brief descriptions of details that are to be accounted for. Such as historical relevance, biological processes, discussions of possible outcomes and announcements of future experiments to explore more issues related to the evolution of innate immunity. In conclusion, it is important to understand that the early human lineage is not fully uncovered, and researchers, such as Deschamps, will continue to publish new findings to piece together the evolutionary connection between archaic and modern humans.