Modern humans have crossed paths with at least five groups of archaic humans

A new study published in the Proceedings of the National Academy of Sciences (PNAS) gives us some details on the so-called blending events that have seen modern men join different groups of archaic humans in the course of their history following their departure from Africa.

It is thought that modern human beings crossed with at least five different archaic human groups in the course of their history that saw them move from Africa through Eurasia to Southeast Asia and beyond. Two of these archaic groups are known: the Neanderthals and the Denisovans group. The others remain unknown although DNA analysis shows the union of our ancestors with other different populations.

In particular, according to the researchers, it was the area of ​​South-East Asia that was a “hotbed of diversity.” As João Teixeira, a researcher at the University of Adelaide, specifies the first author of the study, “These archaic groups were widespread and genetically different and survive in each of us. Their story is an integral part of what we have become.”

An example is given by the fact that today’s populations show in their DNA about 2% of the DNA of the Neanderthals. This, and other genetic data, shows that mixing with Neanderthals must have taken place almost immediately after our ancestors left Africa, in a period between about 50,000 and 55,000 years ago somewhere in the Middle Orient. However, our ancestors, traveling further east, met and mixed with other different groups of humans.

Using various information regarding these migratory routes, the researchers concluded that an important mixing event must have occurred in the areas of southern Asia, in Southeast Asia, with a group that was named “Hominino Estinto 1.” Other crossings, probably of lesser incidence, must then have taken place in East Asia, in the Philippines and near the island of Flores, Indonesia, with another group that the same researchers called “Hominino Estinto 2.”

This information shows that the history of our ancestors once they left Africa seems to be much more complex than I previously deduced and that the South East Asian region played a very important role in the mixing events that led to modern men thanks also to a relative geographical isolation of these populations for hundreds of thousands of years.

Furthermore, this information also suggests that the disappearance of these archaic human populations occurred substantially coinciding with the arrival of modern humans.


Bats use leaves as “mirrors” to understand the presence of resting insects

Bats have a particular localization system that involves sight and hearing to understand, even in darkness, the position of obstacles and even prey, and this is a well-known thing. However, a new study, published in Current Biology, shows how sensitive these animals are through their echolocation system.

Capturing insects and intercepting them in the dark is an impossible task for many, but not for bats. The experiments that the scientists of the Smithsonian Tropical Research Institute (STRI) have conducted, in fact, show that bats are able to trace even acoustically camouflaged prey, that is to say silent prey on the leaves.

Bats are able to hunt these insects thanks to a sort of sixth sense: they flood the surrounding area with sound waves and then use the return echoes to navigate through the environments. However, they also do this with regard to objects of limited extension such as the leaves: the latter reflect the signals and if the latter is a little weaker because there is an insect resting on the bats they can recognize the difference. And this also in a tropical forest, in the thick foliage that characterizes this environment.

Scientists have discovered that if the sound bouncing off the leaves comes from oblique angles greater than 30 degrees, the leaves themselves can behave like “mirrors” like a lake reflects the surrounding forest at dusk at dawn. This means, according to the researchers, that the same angle of approach makes the insect at rest detectable. Therefore the same researchers have deduced that the bats tend to approach the insects that rest on the leaves through angles comprised between 42 and 78 degrees, considered optimal angles to discern the same presence of the insect on the leaf.


New type of pulsating star discovered

A group of scientists from the University of California at Santa Barbara claims to have discovered a new type of pulsating star. This new class of stars seems to vary the brightness every five minutes. In the study, published in the Astrophysical Journal Letters, the researchers, led by Thomas Kupfer, explain the results of their analysis.

In the press release on the university website is Kupfer himself, a researcher at the Kavli Institute for Theoretical Physics (KITP) of the same faculty, to explain the discovery. First of all, he reports that the pulsating stars, or even variable stars, are many and indeed even our Sun, even on a very small scale, performs pulsations. Around a variation of brightness of about 10%, however, we begin to talk about pulsating stars and those that see the major changes in the University are defined radial pulsators that seem to “breathe in and breathe” changing in size.

By studying these mutations in detail, it is possible to learn a great deal about these stars. And that’s exactly what Kupfer did that set out to search for binary stars with pulsation periods of less than an hour. They found four pulsating stars in which great changes in brightness occur within a few minutes and were not binary systems.

Checking the data, they realized that it was a new kind of pulsating stars that had hot button substances. The hot substances are stars that have “completed the fusion of all the hydrogen in their helium nucleus” and this is “because they are so small and can oscillate so quickly,” as stated by Lars Bildsten, director of the KITP and another author of the study.

They are very hot, much warmer than the Sun, although they have a mass between 20 and 50% of that of the same Sun. The pulsating hot substances were never predicted theoretically but, once analyzed, they adapted without problems to the main models of stellar evolution.