Rain Scald: The Future of a New Sexually Transmitted Disease

The Finnish public broadcaster Yle has reported that a new sexually transmitted infection has begun spreading in Europe. In fact, the disease is one that has long been known to affect horses and cattle: rain scald (also known as dermatophilosis). Previously, it had occurred mainly in people who worked closely with these animals, but it has now started to spread to others as well.

The disease is caused by bacteria and produces scaly skin lesions, raised bumps, and pus-filled blisters on various parts of the body. So far, however, it has responded well to antibiotic treatment, and the situation remains under control.

The infection has not been spreading among people engaging in conventional sexual activity. Rather, according to Yle's report, it "is currently found mainly among men who have visited gay saunas in France, Spain, Germany, and Sweden. Transmission has occurred through sexual contact or other forms of close skin-to-skin contact."

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It remains to be seen whether this emerging disease will develop into a genuine epidemic or remain a passing curiosity. In this regard, bisexual men are likely to play a key role, as they could enable the bacterium to cross the gender barrier from gay men to heterosexual women.

If rain scald does begin to spread more widely, another important question will be whether the pathogen starts adapting to humans. In other words, will genetic changes be selected in bacterial strains that circulate between people, making transmission during sexual contact more efficient than it is today?

Should that happen, the next likely development would be the evolution of antibiotic resistance. As a result, treating the disease would become more difficult than it is at present.

For now, we can only wait and see what the future brings. At present, the only certainty is that abstaining from sex, or having sex exclusively with one faithful partner—and, apparently, also using a physical barrier such as a condom—prevents infection.

Previous thoughts on the same topic:
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Evolution in action

Neanderthals Mated with Denisovans, Exceeded Modern Human Diversity

Neanderthals and Denisovans were prehistoric humans who interbred to some extent also with members of the human lineage that led to modern humans. In this context, an international research team – Diyendo Massilani and colleagues – has now published the entire genome extracted from DNA isolated from a Neanderthal fossil that lived about 110,000 years ago. This is the first male genome determined from this species.

The Neanderthal man in question had died in Denisova Cave in the Altai Mountains, the same location where Denisovans also lived at times. According to the research group’s results, the man belonged to a human group that was more closely related to another Neanderthal found in the same cave, who had lived about 10,000 years earlier, than to his counterparts in Europe or to a Neanderthal from another cave in the Altai Mountains who lived about 80,000 years ago.

The genomes of both Neanderthals from Denisova Cave that have now been sequenced contained genes originating from Denisovans, indicating that the species interbred with each other at least in the Altai region more than 100,000 years ago. This was surprising, because later Neanderthals from the Altai region or from Western Europe show no evidence of such interbreeding.

Based on DNA – specifically the extent of homozygous chromosomal regions – it was also possible to conclude that Neanderthals living in the Altai region 120,000–80,000 years ago lived in smaller and more isolated groups than later European Neanderthals (54,000–40,000 years ago). In addition, the researchers observed that the genome sequences of Neanderthals belonging to these populations differed from each other more than the genomes of the most genetically distant modern human populations (the Mbuti of Central Africa and the Highland Papuans of New Guinea).

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The study I have briefly described above is unlikely to be directly applicable for commercial purposes. Instead, it satisfies our curiosity and fulfills our need for knowledge: the opening up of the ancient world is undeniably fascinating.

Perhaps even more important than curiosity and the desire for knowledge, however, is that as science advances, humanity’s awareness of itself and of the world increases. And over time, this influences the way we see ourselves and the world we live in.

It is, of course, true that this perspective does not affect all people in the world equally: there is a significant difference, for example, in how the Taliban in Afghanistan and secularized Europeans perceive the world. Whereas the former are guided by the writings of a prophet and war leader who lived in the 7th century, the latter make their everyday decisions based on modern scientific knowledge—though usually without explicitly realizing it.

The contribution of paleogenomics—the field represented by the study described above—may not be decisive in this broader picture, but it is not negligible either. Awareness of the lives of our ancient relatives in small, isolated populations, their interbreeding with each other—and with our ancestors—and the extinction of those lineages provides important context for understanding present-day humanity and its peoples.

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The Surprising Story of Europe’s Hippos
The Historical Merging of Human Groups
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The Surprising Story of Europe’s Hippos

Hippopotamuses are the largest land animals living today after elephants and rhinoceroses. Today, the species occurs only in Africa, but remains have also been found in Europe.

They have been assumed to originate from the last interglacial period. This assumption is based on the fact that the hippopotamus is considered an indicator species of temperate climates and is thought to have gone extinct north of the Mediterranean at the onset of the Weichselian glaciation around 115,000 years ago.

* * *

A recent study by Patrik Arnold and his colleagues has now brought surprising new insights concerning European hippopotamuses. The researchers analyzed Central European hippopotamuses by sequencing the genome of one individual, which revealed a close genetic relationship between these animals and modern African hippopotamuses.

In addition, they determined six other partial mitochondrial genomes, which confirmed that the European fossils belonged to the same species as present-day African hippopotamuses. The species therefore once had a much wider distribution than today and was not always restricted to sub-Saharan Africa.

The researchers also conducted radiocarbon dating of the fossils and were greatly surprised to discover that they were much more recent than previously believed. The remains dated to the middle phase of the Weichselian glaciation, a period beginning before 47,000 years ago and ending around 31,000 years ago—that is, during the later stages of the last Ice Age.

Because radiocarbon dates of woolly mammoth and woolly rhinoceros fossils from the same sites fall within the same time range, these animals also inhabited Europe at that time. Consequently, the fauna of our continent was very different from what had previously been assumed or from what we know today.

The researchers also analyzed genetic variation in the now fully sequenced hippopotamus genome and found its genetic diversity to be low. It is therefore likely that this individual belonged to a small population that lived in isolation from other hippopotamuses.

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Love and a Regurgitated Gift

In the world of fruit flies, romance can take surprising forms. The species Drosophila subobscura has a peculiar courtship ritual: before mating, a male must win over the female by giving her a gift. But instead of flowers or chocolates, he offers her a tiny mouth-to-mouth meal of regurgitated food. Interestingly, their close cousin Drosophila melanogaster—the fruit fly most often used in laboratories—doesn’t do this at all.

So what makes one species a generous suitor while the other skips the gift exchange? Japanese researchers discovered that the difference comes down to a single gene, called FruitlessM (FruM), which helps wire male brains for courtship behavior. In D. subobscura, this gene switches on in a group of brain cells that regulate feeding. When FruM is missing, the cells don’t grow the connections they need, and the males fail to present their nuptial gift.

Even more intriguing, when scientists turned on FruM in the same brain cells of D. melanogaster, something remarkable happened: the cells sprouted new connections, and the males began regurgitating food more often—hinting at a hidden potential for gift-giving buried in their biology.

This research shows how a small genetic change can spark big differences in behavior between species. What looks like a simple act of food sharing is, in fact, the product of evolutionary history written deep in the wiring of the brain.

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Evolution Doesn’t Just Create New Species – It Can Also Reverse It

When Charles Darwin pondered how a single species could, over time, become two distinct ones, he realized that natural selection could act differently on separate populations, gradually driving them apart. This insight was so powerful that it gave rise to an entirely new scientific field: evolutionary biology.

To this day, the emergence of new species remains a central concept in evolutionary biology, and understanding the mechanisms behind it is one of the field’s key research questions. At the same time, hybridisation between populations that have evolved in isolation can influence the pace of speciation—either speeding it up, slowing it down, or even reversing it altogether.

A recent study by Ingo Müller and colleagues delved into the evolutionary history of Melidectes, a bird genus found in New Guinea that includes six species living in various mountainous regions at different elevations. Most of these species occupy separate areas, but two of them meet and hybridise in the central mountain range.

Despite this overlap, scientists had assumed that differences in plumage and adaptations to elevation would help maintain clear species boundaries. However, Müller and his team used genomic and genetic analyses to show that these visible differences do not, in fact, prevent gene flow between the two species. On the contrary, the researchers discovered that their genes are mixing extensively across most of their shared range.

This makes the bird community formed by these two species quite unusual. It follows a pattern where the most genetically distinct and least interbreeding populations are found at the geographical edges of their ranges. Remarkably, this is the case even though their maternally inherited mitochondrial genomes still sort neatly into two deeply divergent lineages, consistent with their traditional species identities.

These findings led the researchers to conclude that the two incipient species have recently begun to merge—possibly due to increased contact brought on by climate warming—resulting in nearly complete fusion into a single lineage. In other words, a speciation process that was well underway has now stalled, and the two almost-species appear to be on the path to becoming one unified species again.

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The Dire Wolf and the Rights of Extinct Human Species

The Americans have announced that they have brought back to life a dire wolf that lived during the Ice Age. Or, more precisely, they have created a hybrid — a cross between a gray wolf and an ancient dire wolf.

This was made possible by two things. First, the genome of the dire wolf has been successfully determined from fossil material. And second, the general advancement of methods for modifying the DNA of living organisms.

The case is the first of its kind and particularly interesting because the animal species in question is not actually very closely related to the wolf. Instead, it belongs to an entirely different genus within the canine family. Thus, quite a lot of genetic modifications had to be made, and the resulting animals may not — or even likely will not — behave like the original dire wolves.

It remains to be seen what will happen to these hybrid animals in the future. Will they become free predators roaming the North American wilderness, or — as I rather suspect — exhibition pieces harnessed for profit in zoos or even in some kind of traveling shows? It will also be interesting to see whether this revival of the dire wolf will be followed by attempts to bring back other extinct creatures, like mammoths or thylacines.

One thing is certain, however: the creation of these animals will spark lively debate about the ethics of science. And there is little doubt that the most heated discussions will center around humanity’s own relatives.

After all, with the methods that have now been successfully used, it is possible — at least in theory — to also bring back extinct human species. Such as Neanderthals, Denisovans, or even Homo erectus.

If that were to happen, difficult questions would arise. For example, regarding whether they should be granted the same human and civil rights as everyone else.

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Dark Brown Ancestors

Mammals can be colorful, but generally speaking, their brilliance is somewhat more subdued than that of birds. However, fur coloration affects their behavior, physiology, and habitat.

In a recent study conducted by an international research team, the coloration of ancient mammalian ancestors that lived 252–66 million years ago was investigated, as little is known about their coloration despite their coexistence with dinosaurs. The researchers analyzed the shape of pigment-containing organelles and compared them to the fur color of 116 modern mammals.

Through this analysis, they were able to reliably deduce the fur color of six ancient mammal-like creatures. It turned out that, unlike feathered dinosaurs, the melanosome structure of these ancient mammals was quite uniform and likely dark brown. This dark coloration probably helped them blend into their nocturnal environment, as they were primarily active at night.

The study suggests that the more diverse color palette of modern mammals only emerged after the mass extinction of dinosaurs, when mammals began to rapidly evolve and diversify. This is likely due to some mammals adapting to daytime activity, as they were no longer prey for predatory dinosaurs.

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The Historical Merging of Human Groups

Understanding human evolution has progressed step by step during my lifetime. One of the most sensational discoveries was the evidence of interbreeding between Neanderthals, who lived in Europe before modern humans, and our ancestors.

Significant new information has once again been obtained on this matter. It was based on an excellent idea: previously, the focus had been on determining how much Neanderthal DNA is present in our genes, but now researchers decided to investigate how much so-called modern human DNA is present in Neanderthal genes.

This was possible using two criteria. The first was based on the fact that Neanderthals were already known to be much fewer in number than modern humans, so their genomes likely contained less variation. Thus, the more variable regions of the Neanderthal genome would be possible gene regions originating from modern humans.

When such gene regions were then found, the corresponding segments of heritage could be searched for in modern Africans, who have never interbred with Neanderthals. If they had similar genome segments to the now-found more variable regions, they must have developed in modern humans and not in Neanderthals. And indeed, this confirmed that as much as about ten percent of Neanderthal genes ultimately came from modern humans.

Based on this new information, it can also be concluded that Neanderthals may not have disappeared from the world after all but simply merged into the much more numerous populations of modern humans. And they left their genetic mark on them— a set of genes that developed in Neanderthals and have since been passed down to me and to all of you, dear readers, unless you are entirely of African descent.

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The amazing adventures of the German cockroach
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The amazing adventures of the German cockroach

The German cockroach, also known as the common cockroach, is a member of the animal kingdom that brings to mind positive thoughts for few people - hardly even the most enthusiastic animal rights advocates. However, in all its repulsiveness, it is an extremely interesting creature that is entirely dependent on humans, as it is not known to live independently anywhere in the world.

The German cockroach was described by Carl von Linné, who developed the modern system of organism classification. He also suggested that it originated from somewhere else than Europe. And indeed, he was a wise man, for research has shown that the cockroach originated in Asia and has even traced its spread around the world.

By analyzing mitochondrial genes, it has been shown that the German cockroach is most closely related to the Asian cockroach, which was originally described in Japan but has since spread to the United States. The journey of the German cockroach from Asia has been investigated by mapping genomic similarities from 281 samples collected in 17 countries.

Their genetic relationships indicate that German cockroaches achieved global distribution in two waves, both assisted by humans. However, this only began after the ancestors of the German cockroach diverged from the Asian cockroach about 2100 years ago.

This likely happened in India or Myanmar as the cockroaches adapted to eating human food. After mastering this skill, the German cockroach moved to the Middle East about 1200 years ago, coinciding with the expansion of trade and warfare during the two Islamic caliphates, the Umayyads and the Abbasids. The likely means of transportation were bread baskets carried by people.

In the next wave, the species' range expanded to Southeast Asia about 390 years ago, driven by colonial trade by the Dutch and British East India Companies. Finally, trading ships brought the cockroaches to Europe around 300 years ago.

Subsequently, steamships and improved housing – with heating and plumbing creating warm, humid conditions favored by cockroaches – enabled the German cockroach to spread worldwide. The only place left unconquered is Antarctica.

The story of the German cockroach, as briefly described above, illustrates how natural selection takes advantage of opportunities. First, the abundance of food produced by agriculture created a new ecological niche, allowing some cockroaches to specialize in consuming human food.

With the services provided by humans, the cockroaches were then ready to travel with them all over the world. And to adapt to living in the most diverse conditions – as long as there is someone there providing them with bread and warmth.

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Cousin is a cultural delicacy

We Europeans are well aware that among many developing nations, it is common to marry relatives. So the idea is, "the cousinier, the juicier."

What remains unclear, however, is whether this has been the original behavior of humanity or a later cultural development, despite some indications suggesting an increase in consanguineous marriages among humans in recent times.

To get an answer, one must of course examine human groups that lived long ago. And it was precisely such a research report that I recently came across.

The study I read analyzed the last hunter-gatherers inhabiting Western Europe, who soon became displaced by the farming newcomers spreading from the southeast of the continent - or merged with them. The examined individuals had inhabited southern Brittany in France approximately seven or eight thousand years ago.

The analysis of ten individuals from three different locations revealed that spouses were not sought from within their own groups but from among different groups residing in different locations. As a result, consanguineous marriages were avoided, despite the very small population of each group - and consequently, also of the hunter-gatherers living in the area.

Somewhat surprisingly, researchers also found that the hunter-gatherers did not seek spouses from farming communities, even though such communities existed in the vicinity. Thus, the hunter-gatherer communities of the time remained quite separate for a long time, even though there was migration from them to the farming communities.

Returning to the question of cousin marriages that initiated this blogpost, based on the study I've discussed, it can be concluded that the original inhabitants of Europe did not practice such marriages.

In other words, they had an excellent understanding that marrying cousins was not sensible. This seems to be not clear to all contemporary human groups, those who, for one reason or another, have adopted consanguineous reproduction in their culture.

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Long distance trade

Evolution in action

The yellow fever mosquito is responsible for spreading yellow fever, Zika, chikungunya, and dengue viruses, leading to hundreds of millions of infections each year. Although it previously showed no interest in humans and preferred other animals, a new genomic analysis has revealed that the ancestral mosquito species split about 5,000 years ago due to a drying climate in the West African Sahel, transforming the previously prevailing grassland landscapes into a desert.

Researchers compared mosquito genomes collected across Africa and Brazil and discovered another significant migration event when the insect spread from Africa to the Americas. This likely occurred around 1800, during the period when approximately 80 000 enslaved individuals were transported across the ocean annually. Yellow fever mosquitoes laid their eggs in water barrels and fed on the people aboard the ships.

In the absence of water bodies, some mosquitoes likely adapted to laying their eggs in water storage containers in communities, subsequently developing a preference for humans as a food source due to their increased availability compared to other mammals.

The investigation also unveiled rapid and ongoing evolution within the species, allowing for more efficient transmission of diseases in African cities. These evolving mosquitoes may explain recent changes in disease transmission patterns. 

For instance, Burkina Faso experienced its first modern dengue outbreak only seven years ago, yet the problem has resurfaced every year since. Additionally, Ouagadougou's mosquitoes quickly adapted to breeding in public hand-washing services installed during the COVID-19 pandemic.

It remains uncertain whether the evolving mosquito strains will spread beyond Africa. But is is clear anyway, that scientists now have an unprecedented opportunity to observe evolution in action.

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American black population more vulnerable to the Omicron variant of SARS-CoV-2

The spread of the Omicron variant of the SARS-CoV-2 virus has turned the number of COVID-19 cases up again. In Finland, the number of daily deaths have during the last weeks been the highest during the epidemic that started more than two years ago. Globally, however, the number of deaths were higher in January and May 2021. 

Omicron variant is known to cause less serious symptoms compared to previous variants of concern, and thus the death rate per the number of infections is lower. Therefore it was highly interesting to read from the Science magazine about research conducted in the USA on COVID-19 related differences between ethnic groups. 

The leading American science-journal reported that black adults were hospitalized for this disease at four times higher rate compared to white adults. The difference between the two groups was 40% versus 47% after two vaccinations and 44% versus 55% if they were given a booster. However, in both groups the hospital stays for Omicron were shorter compared to those caused by the previously common Delta variant, namely 5 days versus 4 days, and intensive care was not needed that often. 

The question that came to my mind was, whether this racial difference has something to do with the genes from archaic humans, Neanderthals, which do not occur in African groups of people. That was because it was previously noted that in the UK people with South Asian roots died for corona considerably more often that those associated with other ethnic groups - and the explanation was the genetic inheritance from the Neanderthals, which made them more susceptible for the virus. 

It was, however, also noticed that the same genes were rare among people of the easternmost Asia, possibly due to prehistoric selection caused by ancient viruses related to SARS-CoV-2. So, could it be possible, that most people with roots outside Africa, have some - yet unknown - genes associated with a higher tolerance to the Omicron virus? 

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