Researchers shed new light on the origins of modern humans

Researchers from the University of Huddersfield, with colleagues from the University of Cambridge and the University of Minho in Braga, have been using a genetic approach to tackle one of the most intractable questions of all—how and when we became truly human.

Researchers shed new light on the origins of modern humans
Map showing early African archaeological sites with evidence for symbolic material and microlithic stone tools
[Credit: NASA Goddard Space Flight Center Image by Reto Stöckli]

Modern Homo sapiens first arose in Africa more than 300,000 years ago, but there is great controversy amongst scholars about whether the earliest such people would have been ‘just like us’ in their mental capacities—in the sense that, if they were brought up in a family from Yorkshire today, for example, would they be indistinguishable from the rest of the population? Nevertheless, archaeologists believe that people very like us were living in small communities in an Ice Age refuge on the South African coast by at least 100,000 years ago.

Between around 100,000 and 70,000 years ago, these people left plentiful evidence that they were thinking and behaving like modern humans—evidence for symbolism, such as the use of pigments (probably for body painting), drawings and engravings, shell beads, and tiny stone tools called microliths that might have been part of bows and arrows. Some of this evidence for what some archaeologists call “modern human behaviour” goes back even further, to more than 150,000 years.

But if these achievements somehow made these people special, suggesting a direct line to the people of today, the genetics of their modern “Khoi-San” descendants in southern Africa doesn’t seem to bear this out. Our genomes imply that almost all modern non-Africans from all over the world—and indeed most Africans too—are derived from a small group of people living not in South Africa but in East Africa, around 60,000-70,000 years ago. There’s been no sign so far that southern Africans contributed to the huge expansion of Homo sapiens out of Africa and across the world that took place around that time.

That is, until now. The Huddersfield-Minho team of geneticists, led by Professor Martin Richards at Huddersfield and Dr. Pedro Soares in Braga, along with the eminent Cambridge archaeologist Professor Sir Paul Mellars, have studied the maternally-inherited mitochondrial DNA from Africans in unprecedented detail, and have identified a clear signal of a small-scale migration from South Africa to East Africa that took place at just that time, around 65,000 years ago. The signal is only evident today in the mitochondrial DNA. In the rest of the genome, it seems to have been eroded away to nothing by recombination—the reshuffling of chromosomal genes between parents every generation, which doesn’t affect the mitochondrial DNA—in the intervening millennia.

The migration signal makes good sense in terms of climate. For most of the last few hundred years, different parts of Africa have been out of step with each other in terms of the aridity of the climate. Only for a brief period at 60,000-70,000 years ago was there a window during which the continent as a whole experienced sufficient moisture to open up a corridor between the south and the east. And intriguingly, it was around 65,000 years ago that some of the signs of symbolism and technological complexity seen earlier in South Africa start to appear in the east.

The identification of this signal opens up the possibility that a migration of a small group of people from South Africa towards the east around 65,000 years ago transmitted aspects of their sophisticated modern human culture to people in East Africa. Those East African people were biologically little different from the South Africans—they were all modern Homo sapiens, their brains were just as advanced and they were undoubtedly cognitively ready to receive the benefits of the new ideas and upgrade. But the way it happened might not have been so very different from a modern isolated stone-age culture encountering and embracing western civilization today.

In any case, it looks as if something happened when the groups from the South encountered the East, with the upshot being the greatest diaspora of Homo sapiens ever known—both throughout Africa and out of Africa to settle much of Eurasia and as far as Australia within the space of only a few thousand years.

Professor Mellars commented: “This work shows that the combination of genetics and archaeology working together can lead to significant advances in our understanding of the origins of Homo sapiens.”

The study is published in Scientific Reports.

Source: University of Huddersfield [March 20, 2019]

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New Cretaceous fossil sheds light on avian reproduction

A team of scientists led by Alida Bailleul and Jingmai O’Connor from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences reported the first fossil bird ever found with an egg preserved inside its body. Their findings were published in Nature Communications.

New Cretaceous fossil sheds light on avian reproduction
Photograph of the holotype of Avimaia schweitzerae
[Credit: Barbara Marrs]

The new specimen, representing a new species, Avimaia schweitzerae, was discovered in 110-million-year-old deposits in northwestern China. It belongs to a group called the Enantiornithes (“opposite birds”), which were abundant all around the world during the Cretaceous and co-existed with the dinosaurs.

The new fossil is incredibly well preserved, including the remains of an egg inside its abdomen. Because the specimen is crushed flat, it was only after a small fragment was extracted and analyzed under the microscope that the team realized that the unusual tissue was an egg.

Detailed analysis of the eggshell fragment revealed a number of interesting facts indicating the reproductive system of this female bird was not behaving normally: The egg shell consists of two layers instead of one as in normal healthy bird eggs, indicating the egg was retained too long inside the abdomen.

This condition often occurs in living birds as a result of stress. The unlaid egg then gets coated in a second layer (or sometimes more) of eggshell. This abnormality has also been documented in sauropod dinosaurs, as well as in many fossil and living turtles.

In addition, the eggshell preserved in Avimaia was extremely thin – thinner than a sheet of paper – and did not show the correct proportions of healthy eggs. (Note that avian eggshells consist of three sublayers with particular dimensions.)

These abnormalities suggest that the preserved egg may have been the cause of death of this “mother bird.” Egg-binding, in which the egg becomes stuck inside the body causing death, is a serious and lethal condition that is fairly common in small birds undergoing stress.

New Cretaceous fossil sheds light on avian reproduction
The female individual dead in the water on the left (with an unlaid egg not visible inside its abdomen),
 represents the fossilized individual described here [Credit: Michael Rothman]

Despite being malformed, the egg is excellently preserved, including parts of the eggshell that are rarely seen in the fossil record, such as traces of the egg membrane and the cuticle, which are mostly made of proteins and other organic materials.

Scanning electron microscopy revealed that the cuticle (the outer most protective layer of the eggshell) was made up of very small spherules of minerals. This type of cuticle morphology would be expected for birds that partially burry their eggs, as it has already been proposed to be the case for enantiornithines (Fig. 2). Finding this morphology in Avimaia also supports the hypothesis that a cuticle with protective spherules represents the ancestral condition for avian eggs.

Female birds about to lay eggs deposit a unique bone tissue found inside the empty spaces of their skeleton, which serves as a calcium reservoir for the developing eggshell. Some researchers have argued that this tissue, called medullary bone, is present in other fossils (e.g., other fossil birds), as well as some non-avian dinosaurs and pterosaurs. However, some of these identifications were ambiguous.

Analysis of a fragment of leg bone from the new specimen revealed the presence of medullary bone. Avimaia is the only Mesozoic fossil in which additional morphological evidence of reproductive activity (i.e., the egg) supports the identification of medullary bone.

The preserved egg allows the specimen to be unequivocally identified as female, allowing scientists to test current hypotheses regarding sexual dimorphism (differences between genders).

This new specimen is arguably one of the most interesting Cretaceous fossil birds yet discovered, providing more reproductive information than any other Mesozoic fossil bird.

Source: Chinese Academy of Sciences [March 20, 2019]

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Fragment of clay jar depicting a human face discovered in Jerusalem

A fragment of a pottery jar decorated with a human face dating back to the Persian period was discovered in excavations in Jerusalem. This is the first time such a vessel has been found in Jerusalem or any site in the Judean highlands.

Fragment of clay jar depicting a human face discovered in Jerusalem
The fragment of a Persian-period (4th – 5th century BCE) Bes-Vessel was discovered
 in a large refuse pit in the City of David’s Givati Parking Lot dig, in Jerusalem
[Credit: (c) City of David/Eliyahu Yanai]

In honour of Purim, a fragment of a clay jar decorated with a human face of which two wide open eyes, a nose, one ear and a small section of the corner of the mouth survived. The shard, dated to the Persian period (4th – 5th century BCE) was revealed to the public, after being discovered in archaeological excavations by the Israel Antiquities Authority and Tel Aviv University in the Givati Parking Lot excavation in the City of David​ in a large refuse pit that contained numerous other pottery fragments that dated to the Persian period.
According to Prof. Yuval Gadot of Tel Aviv University and Dr. Yiftah Shalev of the Israel Antiquities Authority, “Pottery from this period was exposed in the past in the City of David​, but this is the first time that such a vessel has been found in archaeological excavations in Jerusalem or anywhere in the Judean highlands.”

Fragment of clay jar depicting a human face discovered in Jerusalem
Credit: (c) City of David/Eliyahu Yanai

These jars are called “Bes-Vessels,” and they were very common during the Persian period. In Egyptian mythology, Bes is the protector deity of households, especially mothers, women in childbirth, and children. Over time, he became regarded as the defender of everything good. He also became associated with music and dancing. His figure adorned the walls of houses and various vessels (pottery and various everyday objects, such as mirrors), or worn as an amulet around the neck. Bes usually appears as a kind of bearded dwarf with a large face, protruding eyes and tongue sticking out when he is wearing a feather hat. This grotesque figure is apparently intended to evoke joy and laughter and drive away the evil spirits.
The figure of Bes as a protector was apparently adopted by the Phoenicians, and many such amulets and Bes vessels have been found in numerous Persian Period settlements along the coast. Such vessels and amulets were also found in Persia itself, in Shushan, Persepolis and other cities, reaching there by Egyptian craftsmen who operated there as part of the international trade economy of the period.

Source: Israel Ministry of Foreign Affairs [March 19, 2019]

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