Human evolution is still happening – possibly faster than ever

Modern medicine’s ability to keep us alive makes it tempting to think human evolution may have stopped. Better healthcare disrupts a key driving force of evolution by keeping some people alive longer, making them more likely to pass on their genes. But if we look at the rate of our DNA’s evolution, we can see that human evolution hasn’t stopped – it may even be happening faster than before.

Human evolution is still happening – possibly faster than ever
Yes, we’re still evolving [Credit: watchara/Shutterstock]

Evolution is a gradual change to the DNA of a species over many generations. It can occur by natural selection, when certain traits created by genetic mutations help an organism survive or reproduce. Such mutations are thus more likely to be passed on to the next generation, so they increase in frequency in a population. Gradually, these mutations and their associated traits become more common among the whole group.

By looking at global studies of our DNA, we can see evidence that natural selection has recently made changes and continues to do so. Though modern healthcare frees us from many causes of death, in countries without access to good healthcare, populations are continuing to evolve. Survivors of infectious disease outbreaks drive natural selection by giving their genetic resistance to offspring. Our DNA shows evidence for recent selection for resistance of killer diseases like Lassa fever and malaria. Selection in response to malaria is still ongoing in regions where the disease remains common.

Humans are also adapting to their environment. Mutations allowing humans to live at high altitudes have become more common in populations in Tibet, Ethiopia, and the Andes. The spread of genetic mutations in Tibet is possibly the fastest evolutionary change in humans, occurring over the last 3,000 years. This rapid surge in frequency of a mutated gene that increases blood oxygen content gives locals a survival advantage in higher altitudes, resulting in more surviving children.

Diet is another source for adaptations. Evidence from Inuit DNA shows a recent adaptation that allows them to thrive on their fat-rich diet of Arctic mammals. Studies also show that natural selection favouring a mutation allowing adults to produce lactase – the enzyme that breaks down milk sugars – is why some groups of people can digest milk after weaning. Over 80% of north-west Europeans can, but in parts of East Asia, where milk is much less commonly drunk, an inability to digest lactose is the norm. Like high altitude adaptation, selection to digest milk has evolved more than once in humans and may be the strongest kind of recent selection.

Human evolution is still happening – possibly faster than ever
Evolution explains why we can still drink milk [Credit: CNN]

We may well be adapting to unhealthy diets too. One study of family genetic changes in the US during the 20th century found selection for reduced blood pressure and cholesterol levels, both of which can be lethally raised by modern diets.

Yet, despite these changes, natural selection only affects about 8% of our genome. According to the neutral evolution theory, mutations in the rest of the genome may freely change frequency in populations by chance. If natural selection is weakened, mutations it would normally purge aren’t removed as efficiently, which could increase their frequency and so increase the rate of evolution.

But neutral evolution can’t explain why some genes are evolving much faster than others. We measure the speed of gene evolution by comparing human DNA with that of other species, which also allows us to determine which genes are fast-evolving in humans alone. One fast-evolving gene is human accelerated region 1 (HAR1), which is needed during brain development. A random section of human DNA is on average more than 98% identical to the chimp comparator, but HAR1 is so fast evolving that it’s only around 85% similar.

Though scientists can see these changes are happening – and how quickly – we still don’t fully understand why fast evolution happens to some genes but not others. Originally thought to be the result of natural selection exclusively, we now know this isn’t always true.

Human evolution is still happening – possibly faster than ever
Biased DNA repairs can cause fast evolution of genes [Credit: Ravil Sayfullin/Shutterstock]

Recently attention has focused on the process of biased gene conversion, which occurs when our DNA is passed on via our sperm and eggs. Making these sex cells involves breaking DNA molecules, recombining them, then repairing the break. However, molecular repairs tend to happen in a biased manner.

DNA molecules are made with four different chemical bases known as C, G, A and T. The repair process prefers to make fixes using C and G bases rather than A or T. While unclear why this bias exists, it tends to cause G and C to become more common.

Increases in G and C at DNA’s regular repair sites causes ultrafast evolution of parts of our genome, a process easily mistaken for natural selection, since both cause rapid DNA change at highly localised sites. About a fifth of our fastest evolving genes, including HAR1, have been affected by this process. If the GC changes are harmful, natural selection would normally oppose them. But with selection weakened, this process could largely go unchecked and could even help speed up our DNA’s evolution.

The human mutation rate itself may also be changing. The main source of mutations in human DNA is the cell division process that creates sperm cells. The older males get, the more mutations occur in their sperm. So if their contribution to the gene pool changes – for example, if men delay having children – the mutation rate will change too. This sets the rate of neutral evolution.

Realising evolution doesn’t only happen by natural selection makes it clear the process isn’t likely to ever stop. Freeing our genomes from the pressures of natural selection only opens them up to other evolutionary processes – making it even harder to predict what future humans will be like. However, it’s quite possible that with modern medicine’s protections, there will be more genetic problems in store for future generations.

Author: Laurence D. Hurst | Source: The Conversation [November 14, 2018]

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Extended life for ESA’s science missions

ESA – European Space Agency patch.

14 November 2018

ESA’s Science Programme Committee (SPC) has confirmed the continued operations of ten scientific missions in the Agency’s fleet up to 2022.

After a comprehensive review of their scientific merits and technical status, the SPC has decided to extend the operation of the five missions led by ESA’s Science Programme: Cluster, Gaia, INTEGRAL, Mars Express, and XMM-Newton. The SPC also confirmed the Agency’s contributions to the extended operations of Hinode, Hubble, IRIS, SOHO, and ExoMars TGO.

This includes the confirmation of operations for the 2019–2020 cycle for missions that had been given indicative extensions as part of the previous extension process, and indicative extensions for an additional two years, up to 2022 [1].

The decision was taken during the SPC meeting at ESA’s European Space Astronomy Centre near Madrid, Spain, on 14 November.

ESA’s science missions have unique capabilities and are prolific in their scientific output. Cluster, for example, is the only mission that, by varying the separation between its four spacecraft, allows multipoint measurements of the magnetosphere in different regions and at different scales, while Gaia is performing the most precise astrometric survey ever realised, enabling unprecedented studies of the distribution and motions of stars in the Milky Way and beyond.

ESA fleet in the Solar System

Many of the science missions are proving to be of great value to pursue investigations that were not foreseen at the time of their launch. Examples include the role of INTEGRAL and XMM-Newton in the follow-up of recent gravitational wave detections, paving the way for the future of multi-messenger astronomy, and the many discoveries of diverse exoplanets by Hubble.

Collaboration between missions, including those led by partner agencies, is also of great importance. The interplay between solar missions like Hinode, IRIS and SOHO provides an extensive suite of complementary instruments to study our Sun; meanwhile, Mars Express and ExoMars TGO are at the forefront of the international fleet investigating the Red Planet.

Another compelling factor to support the extension is the introduction of new modes of operation to accommodate the evolving needs of the scientific community, as well as new opportunities for scientists to get involved with the missions.

[1] Every two years, all missions whose approved operations end within the following four years are subject to review by the advisory structure of the Science Directorate. Extensions are granted to missions that satisfy the established criteria for operational status and science return, subject to the level of financial resources available in the science programme. These extensions are valid for the following four years, subject to a mid-term review and confirmation after two years.

Related links:

ESA’s Cluster: http://sci.esa.int/cluster

ESa’s Gaia: http://sci.esa.int/gaia

ESA’s INTEGRAL: http://sci.esa.int/integral

ESA’s Mars Express: http://sci.esa.int/mars-express

ESA’s XMM-Newton: http://sci.esa.int/xmm-newton

ESA’s collaboration:

ESA’s Hinode: http://www.isas.jaxa.jp/en/missions/spacecraft/current/hinode.html

ESA’s Hubble: http://sci.esa.int/hubble

ESA’s IRIS: https://www.nasa.gov/mission_pages/iris/index.html

ESA’s SOHO: http://sci.esa.int/soho

ESA’s ExoMars TGO: http://exploration.esa.int/mars

Image, Text, Credits: ESA/Luigi Colangeli.

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Not so dangerous: Neanderthals and early modern humans show similar levels of cranial injuries

A team of University of Tübingen researchers led by Professor Katerina Harvati has shown that Neanderthals sustained similar levels of head injuries to the earliest anatomically modern humans in Eurasia. This result contradicts previous views that Neanderthals were characterized by exceptionally high rates of trauma. The study, authored by scientists from Paleoanthropology, Senckenberg Centre for Human Evolution and Palaeoenvironment, and the Institute of Evolution and Ecology at the University of Tübingen, is published in Nature.

Not so dangerous: Neanderthals and early modern humans show similar levels of cranial injuries
Neanderthals are commonly thought to have relied on dangerous close range hunting techniques,
using non-projectile weapons like the thrusting spears depicted here
[Credit: Gleiver Prieto & Katerina Harvati]

The life of Neanderthals, who lived in western Eurasia from approximately 400,000 to 40,000 years ago, has long been portrayed as harsh and dangerous. This view is in part based on unusually high incidence of traumatic injuries described for Neanderthal fossils. Neanderthal injuries are thought to be most often concentrated on the head and to result from several possible causes, including violent social behavior, a mobile hunter-gatherer-lifestyle in Ice Age environments where accidents would be common, and attacks by carnivores such as cave bears or cave hyenas.
Importantly, Neanderthals are thought to have relied on close range weapons, such as stabbing or thrusting spears, and therefore to have repeatedly come into close range confrontations with large prey animals during hunting. High levels of head injury in Neanderthals, therefore, have been used to infer not only dangerous lifestyles, but also violent behavior and inferior hunting techniques. Until now, however, these inferences were mainly based on case by case reports of injuries on specific individual skeletons, rather than on population-wide statistical analyses.

In their new study the Tübingen scientists applied a quantitative, population-wide analysis of head trauma among Neanderthals and Upper Paleolithic modern humans from Western Eurasia to test this hypothesis. They used a newly compiled database of several hundred fossil specimens, both with and without injuries, and rigorous statistical modelling accounting for sex, age at death, geography and state of preservation of the bones. None of their models revealed significant differences in trauma prevalence between the two groups.

Not so dangerous: Neanderthals and early modern humans show similar levels of cranial injuries
Neanderthal (left) and modern human skeleton. Neanderthals have commonly be
considered to show high incidences of trauma compared to modern humans
[Credit: Ian Tattersall]

“Our findings refute the hypothesis that Neanderthals were more prone to head injuries than modern humans, contrary to common perception”, explains Professor Katerina Harvati. “We therefore believe that the commonly cited Neanderthal behaviors leading to high injury levels, such as violent behavior and inferior hunting capabilities, must be reconsidered.”

The researchers found that males were more frequently injured than females among both Neanderthals and early modern humans, a finding consistent with observations in more recent human groups, explained by division of labor between men and women or by other culturally determined sex-specific behaviors and activities. Beyond these similarities, the researchers also found interesting differences.

“While Neanderthals and Upper Paleolithic modern humans exhibited a similar prevalence of trauma overall, we found a different age-related trauma prevalence for each species”, explains Judith Beier, first author of the study. This could mean that Neanderthals were more likely to be injured at a younger age than Upper Paleolithic modern humans. Alternatively, it could be related to differences in long-term survival after a (non-lethal) injury.

“The age-related pattern is a novel finding”, explains Harvati. “Overall, however, our results suggest that Neanderthal lifestyles were not more dangerous than those of our ancestors, early modern Europeans.”

Source: Universität Tübingen [November 14, 2018]

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