If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.
Neanderthals, who died out 40,000 years ago, and Homo sapiens shared a common ancestor before taking separate evolutionary paths. Both are large brained (in fact, Neanderthals had a larger cranial capacity), but body form is quite different, with our cousins having a more robust skeletal frame.
The longer period of brain and spine development in Neanderthals is due to their large body and physiology, Rosas says. The extended time should not be construed as a fundamental difference in growth pattern to that of modern humans.
The boy was found in El Sidrón, a complex cave system in Asturias, Spain, that has given up the remains of seven adults and six children, all within the same Neanderthal group. Many appear to be kin, the paper says. Ancient DNA samples suggest the boy might have had an infant sibling. Both could be offspring of a young adult female also found in the cave.
A skeletal examination suggests that the boy was 3 feet, 6 inches tall and weighed about 57 pounds — a formidable frame. He was generally healthy, Rosas says, though he endured a period of stunted growth, which can happen from deficiencies in nutrition. “He was starting to do daily activities,” Rosas says.
And then he died. “No evidence of trauma or disease,” Rosas says. “Cause of death is unknown.”
The researchers plan to also examine other remains of Neanderthal children in El Sidrón. “This will be the first step to get a bigger picture of the life cycle of Neanderthals,” Rosas says.
Jo Bowyer Chartered Physiotherapist Registered Osteopath. "Out beyond ideas of wrongdoing and rightdoing,there is a field. I'll meet you there." Rumi
The study, reported in the journal Science, examined genetic information from the remains of anatomically modern humans who lived during the Upper Palaeolithic, a period when modern humans from Africa first colonised western Eurasia. The results suggest that people deliberately sought partners beyond their immediate family, and that they were probably connected to a wider network of groups from within which mates were chosen, in order to avoid becoming inbred.
This suggests that our distant ancestors are likely to have been aware of the dangers of inbreeding, and purposely avoided it at a surprisingly early stage in prehistory.
The symbolism, complexity and time invested in the objects and jewellery found buried with the remains also suggests that it is possible that they developed rules, ceremonies and rituals to accompany the exchange of mates between groups, which perhaps foreshadowed modern marriage ceremonies, and may have been similar to those still practised by hunter-gatherer communities in parts of the world today.
The study's authors also hint that the early development of more complex mating systems may at least partly explain why anatomically modern humans proved successful while other species, such as Neanderthals, did not. However, more ancient genomic information from both early humans and Neanderthals is needed to test this idea.
Jo Bowyer Chartered Physiotherapist Registered Osteopath. "Out beyond ideas of wrongdoing and rightdoing,there is a field. I'll meet you there." Rumi
After humans and Neanderthals met many thousands of years ago, the two species began interbreeding. Recent studies have shown that some of those Neanderthal genes have contributed to human immunity and modern diseases. Now researchers have found that our Neanderthal inheritance has contributed to other characteristics, too, including skin tone, hair color, sleep patterns, mood, and even a person's smoking status.
Jo Bowyer Chartered Physiotherapist Registered Osteopath. "Out beyond ideas of wrongdoing and rightdoing,there is a field. I'll meet you there." Rumi
The Altai and Vindija genomes are remarkably similar and that limited genetic diversity suggests that Neandertals lived in small, isolated populations of about 3000 individuals of reproductive age, Prüfer says. "This speaks to debates about why they went extinct," Capra says. "They probably were less robust in their response to disease, starvation, and changes in climate."
Jo Bowyer Chartered Physiotherapist Registered Osteopath. "Out beyond ideas of wrongdoing and rightdoing,there is a field. I'll meet you there." Rumi
We are all descended from astronomers,’ the astrophysicist Neil deGrasse Tyson intones in the rebooted version of the TV show Cosmos. This is as poetic as it is true. Everyone owns the night sky; it was the one natural realm all our ancestors could see and know intimately. No river, no grand mountain or canyon, not even the oceans can claim that. But since Edison’s light bulbs colonised our cities, the vast majority of humans has ceased to see those skies.
Jo Bowyer Chartered Physiotherapist Registered Osteopath. "Out beyond ideas of wrongdoing and rightdoing,there is a field. I'll meet you there." Rumi
Many in modern cultures grow up believing a myth about lifelong love. We are told about falling for the one and only. We learn that the path to fulfilment is paved with a single glorious union. But the plots of fictional love stories often come to a close upon the discovery of that one and only, and rarely examine the aftermath. The story of Cinderella ends with her getting the prince. After overcoming countless obstacles, a union is finally consummated. Few romantic fantasies follow the storyline of committed mating – the gradual inattentiveness to each other’s needs, the steady decline in sexual satisfaction, the exciting lure of infidelity, the wonder about whether the humdrum greyness of married life is really all life has to offer.
In fact, we come from a long and unbroken line of ancestors who went through mating crises – ancestors who monitored mate value, tracked satisfaction with their current unions, cultivated back-ups, appraised alternatives, and switched mates when conditions proved propitious.
Evolution did not design humans for lifelong matrimonial bliss. Our ancestors faced a mating world where something could always go wrong. Those who stuck it out through thick and thin might win admiration for their loyalty. But modern humans have descended from successful ancestors who carried mate insurance; who devoted energy to scenario-building, the cognitive simulations of fantasising about possible mates and laying plans for exiting; and who acted on those scenarios when the hidden calculus pointed to the benefits of switching mates.
Jo Bowyer Chartered Physiotherapist Registered Osteopath. "Out beyond ideas of wrongdoing and rightdoing,there is a field. I'll meet you there." Rumi
The first modern humans arose in Africa about 300,000 years ago. By 60,000 years ago, a subset swept out of Africa and mated with Neandertals, perhaps in the Middle East. After that, they spread around the world—DNA from ancient humans in Europe, western Asia, and the Americas has revealed the identity of those early migrants and whether they were related to people living today, especially in Europe. But the trail grows cold in eastern Asia, where warmer climates have made it hard to get ancient DNA from fossils.
The new genome sheds some light on those missing years. In the first genome-wide study of an ancient East Asian, researchers led by Qiaomei Fu, a paleogeneticist at the Chinese Academy of Sciences in Beijing, extracted DNA from the thighbone of the Tianyuan Man—so named because he was found in Tianyuan Cave, 56 kilometers southwest of Beijing.
The team calculated that the Tianyuan Man inherited about as much Neandertal DNA—4% to 5%—as ancient Europeans and Asians of similar age. That’s a bit higher than the 1.8% to 2.6% of Neandertal DNA in living Europeans and Asians. The Tianyuan Man did not have any detectable DNA from Denisovans, an elusive cousin of Neandertals known only from their DNA extracted from a few teeth and small bones from a Siberian cave and from traces of their DNA that can still be found in people in Melanesia—where they got it is a major mystery.
A big surprise is that the Tianyuan Man shares DNA with one ancient European—a 35,000-year-old modern human from Goyet Caves in Belgium. But he doesn’t share it with other ancient humans who lived at roughly the same time in Romania and Siberia—or with living Europeans. But the Tianyuan Man is most closely related to living people in east Asia—including in China, Japan, and the Koreas—and in Southeast Asia, including Papua New Guinea and Australia.
All of this suggests that the Tianyuan Man was not a direct ancestor, but rather a distant cousin, of a founding population in Asia that gave rise to present-day Asians, Fu’s team reports today in Current Biology. It also shows that these ancient “populations moved around a lot and intermixed,” says paleoanthropologist Erik Trinkaus of Washington University in St. Louis in Missouri, who is not a co-author.
Jo Bowyer Chartered Physiotherapist Registered Osteopath. "Out beyond ideas of wrongdoing and rightdoing,there is a field. I'll meet you there." Rumi
When Neandertals mated with modern humans, they shared more than an intimate moment and their own DNA. They also gave back thousands of ancient African gene variants that Eurasians had lost when their ancestors swept out of Africa in small bands, perhaps 60,000 to 80,000 years ago. Restored to their lineage, this diversity may have been a genetic gift to Eurasian ancestors as they spread around the world. Today, however, some of these African variants are a burden: They seem to boost the risk of becoming addicted to nicotine and having wider waistlines.
In talks last week at the annual meeting of The American Society of Human Genetics here, researchers announced that some “Neandertal” genetic variants inherited by modern humans outside of Africa are not peculiarly Neandertal genes, but represent the ancestral human condition. The work highlights just how much diversity was lost when people passed through a genetic bottleneck as they moved out of Africa.
“They left many beneficial variants behind in Africa,” says evolutionary genomicist Tony Capra of Vanderbilt University in Nashville, who reported the results. “Interbreeding with Neandertals provided an opportunity to get back some of those variants, albeit with many potentially weakly deleterious Neandertal alleles as well.”
His team found the ancient African variants when they scrutinized the genomes of more than 20,000 people in the 1000 Genomes Project and Vanderbilt’s BioVU data bank of electronic health records. They soon noticed a strange pattern: Stretches of chromosomes inherited from Neandertals also carried ancient alleles, or mutations, found in all the Africans they studied, including the Yoruba, Esan, and Mende peoples. The researchers found 47,261 of these single-base changes across the genomes of Europeans and 56,497 in Asians, Capra says. In Eurasians these alleles are only found next to Neandertal genes, suggesting all this DNA was inherited at the same time, when the ancestors of today’s Eurasians mated with Neandertals roughly 50,000 years ago.
The most parsimonious explanation is that these alleles represent the ancestral human condition, inherited by both Neandertals and modern humans in Africa from their common ancestor, Capra says. When people migrated out of Africa, their small numbers resulted in a bottleneck, in which they lost many alleles that remained in larger populations in Africa. Later, the Neandertals reintroduced these alleles—along with distinct Neandertal genes—to the ancestors of Eurasians, Capra says. Some of these ancient alleles were beneficial, such as one that boosted immune responses.
Jo Bowyer Chartered Physiotherapist Registered Osteopath. "Out beyond ideas of wrongdoing and rightdoing,there is a field. I'll meet you there." Rumi
What made us human? Gene expression changes clearly played a significant part in human evolution, but pinpointing the causal regulatory mutations is hard. Comparative genomics enabled the identification of human accelerated regions (HARs) and other human-specific genome sequences. The major challenge in the past decade has been to link diverged sequences to uniquely human biology. This review discusses approaches to this problem, progress made at the molecular level, and prospects for moving towards genetic causes for uniquely human biology.
Post-genomic challenges for determining uniquely human biology
When the human genome was first sequenced [1, 2], the big question was “how many genes do we have?” Most people guessed too high. Sequencing our closest living relative, the chimpanzee [3, 4], begged the question “which genes are different?” Here the answer was predicted a century before and supported by King and Wilson’s 1975 discovery that certain blood proteins have very few amino acid differences between human and chimpanzee [5, 6]. We now know that the vast majority of all genomic changes that happened since the human–chimpanzee ancestor are in non-coding regions, consistent with King and Wilson’s hypothesis that regulatory changes drove the differences between our species. In hindsight, the importance of gene regulation in human evolution is logical. There are many more DNA bases in regulatory regions than in protein-coding genes, making them a larger target for evolutionary innovation. Furthermore, genes frequently function in many different contexts, and this pleiotropy constrains their evolution compared to regulatory elements, which tend to be more modular [7]. Thus, regulatory sequences have great potential to be drivers of human evolution.
Jo Bowyer Chartered Physiotherapist Registered Osteopath. "Out beyond ideas of wrongdoing and rightdoing,there is a field. I'll meet you there." Rumi
In this question and answer article we discuss how evolution shapes morphology (the shape and pattern of our bodies) but also how learning about morphology, and specifically how that morphology arises during development, can shed light on mechanisms that might allow change during evolution. For this we concentrate on recent findings from our lab on how the middle ear has formed in mammals.How does evolution help us understand morphology?
Evolution is key to understanding why we look like we do: it can explain why humans have four limbs each with five digits, two forward facing camera eyes, and a mouth full of teeth of different shapes compared to why fruit flies have six limbs plus two wings, two compound eyes, and a proboscis for a mouth. Our anatomy has been slowly shaped over millions of years, and an understanding of evolutionary history can help explain the similar pattern of bones observed in vertebrate limbs. Humans, bats, reptiles and whales evolved from a common ancestor, and the developmental programme to make limbs is shared across these animals and is based on that of this common ancestor. Although the limbs of vertebrates have diverged functionally into the wings of bats, the arms of humans, the forelimbs of reptiles and the fins of whales, they are nevertheless homologous: the general skeletal structure is similar in each, despite large differences in individual bone size and shape (Fig. 1). In contrast, the common ancestor of humans and fruit flies did not have any limbs, so our limbs and the limbs of the fly are independently evolved and not homologous.
You mentioned the middle ear—what’s the difference between the middle ear in reptiles, birds and mammals?
The ears of reptiles, birds and mammals are made up of three components. These are the outer ear through which sound in the form of vibrating air enters the head, the inner ear in which sound is converted into neuronal signals by vibration of hair cells lining the cochlea, and the middle ear that sits between the two structures.
The middle ear is an impedance matching apparatus that facilitates the transmission of sound from the air (low impedance) to the liquid filled inner ear (high impedance). The middle ear consists of the tympanic membrane (ear-drum) for sound capture that is connected to a membrane window into the inner ear via small bones called ossicles. In birds and reptiles there is a single ossicle, called the stapes or columella, whereas mammals have a chain of ossicles, the malleus, incus and stapes (Fig. 2) [3]. In both cases the middle ear ossicle or ossicles are in an air-filled cavity that allows for free vibration and transfer of sound to the inner ear. In whales and aquatic mammals, this air-filled cavity is still present but in addition to sound transfer through the three ossicles, bone and soft tissue conduction occurs through the lower jaw to aid with underwater hearing. A more extreme reliance on bone conduction is observed in snakes. Here the middle ear cavity has been lost and is filled with tissue that surrounds the stapes. The tympanic membrane and external ear are absent and instead sound is detected as vibrations by the lower jaw [3].
Why does the middle ear differ between mammals and other amniotes?
The extra ossicles of the mammalian middle ear have a surprising origin. The common amniote’s ancestor did not have a tympanic ear—that is to say they had no tympanic membrane or air filled middle ear—and sound was heard by the vibration of bones embedded in tissue connected to the inner ear. In the mammalian lineage of mammal-like reptiles, changes in the jaw musculature and teeth resulted in the evolution of a new jaw articulation (the temporomandibular joint; TMJ) between the squamosal and dentary bones. This new jaw joint appears to have aided stabilisation of the jaw and initially worked together with the original primary jaw joint, located between the quadrate in the cranial base and articular in the mandible. The fossil record reveals examples of mammal-like reptiles, such as Morganucodon, which used both joints to articulate its jaw. The increased efficiency of the new jaw joint allowed the primary joint to become less integrated into the jaw over time, and as a consequence the bones of the jaw reduced in size and were freed up for a new role in hearing. Eventually the primary jaw joint separated completely from the lower jaw. This final separation gave rise to the definitive mammalian middle ear, with the articular being homologous to the malleus, and the quadrate to the incus. The two extra ossicles in the mammalian ear were therefore repurposed from the jaw joint of reptiles—a rather remarkable change in function.
Jo Bowyer Chartered Physiotherapist Registered Osteopath. "Out beyond ideas of wrongdoing and rightdoing,there is a field. I'll meet you there." Rumi
A mysterious cache of bones, recovered from a deep chamber in a South African cave, is challenging long-held beliefs about how a group of bipedal apes developed into the abstract-thinking creatures that we call ‘human’. The fossils were discovered in 2013 and were quickly recognised as the remains of a new species unlike anything seen before. Named Homo naledi, it has an unexpected mix of modern features and primitive ones, including a fairly small brain. Arguably the most shocking aspect of Homo naledi, though, concerned not the remains themselves but rather their resting place.
The chamber where the bones were found is far from the cave entrance, accessible only through a narrow, difficult passage that is completely shrouded in darkness. Scientists believe the chamber has long been difficult to access, requiring a journey of vertical climbing, crawling and tight squeezing through spaces only 20 cm across. It would be an impossible place to live, and a highly unlikely location for many individuals to have ended up by accident. Those details pushed the research team toward a shocking hypothesis: despite its puny brain, Homo naledi purposefully interred its dead. The cave chamber was a graveyard, they concluded.
For anthropologists, mortuary rituals carry an outsize importance in tracing the emergence of human uniqueness – especially the capacity to think symbolically. Symbolic thought gives us the ability to transcend the present, remember the past, and visualise the future. It allows us to imagine, to create, and to alter our environment in ways that have significant consequences for the planet. Use of language is the quintessential embodiment of such mental abstractions, but studying its history is difficult because language doesn’t fossilise. Burials do.
Burials provide a hard, material record of a behaviour that is deeply spiritual and meaningful. It allows scientists to trace the emergence of beliefs, values and other complex ideas that appear to be uniquely human. Homo sapiens is unquestionably unlike any other species alive today. Pinpointing what separates us from the rest of nature is surprisingly difficult, however.
The paradox is that humans are also unquestionably a part of nature, having evolved alongside with all the rest of life. Anthropologists have narrowed in on one singular human feature in particular: the capacity to think in the abstract. Our ability to imagine and communicate ideas about things that are not immediately in front of us is a complex cognitive process, scientists argue, one that is remarkably different from simple, primitive communication about nearby food or imminent danger.
Jo Bowyer Chartered Physiotherapist Registered Osteopath. "Out beyond ideas of wrongdoing and rightdoing,there is a field. I'll meet you there." Rumi
Granting special status to ancient pastoralists as civilization builders is not a new idea. In the 1950s and 1960s, prominent archaeologists argued that horse-riding pastoralists launched a series of migrations out of their homeland, the Pontic-Caspian steppe region north of the Black Sea, from roughly 6,000 to 3,000 years ago. Those archaeologists saw these pastoralists as fierce nomadic warriors who spread the lifestyle, beliefs and language of what is known as Kurgan culture to farmers and foragers in Europe and parts of Asia. Kurgan groups, which included the Yamnaya, were known for burying their people in graves covered by dirt mounds. These groups had no writing system but spoke an early version of modern Indo-European languages, some archaeologists have argued. Indo-European tongues today include English, Spanish, Russian and Bengali, among more than 400 others.
By the 1980s, a different perspective took hold. Researchers proposed that Bronze Age European cultures and languages changed as ideas passed from one group to another. Europeans didn’t form families with wayfaring, or marauding, pastoralists. Instead, locals adopted outsiders’ practices as needed, but the natives kept their genes to themselves.
Proponents of that “migrating ideas” perspective take a cautious view of Yamnaya DNA in Europe. Genetic signatures of past migrations raise more questions than they answer, these researchers argue. DNA can’t comment on why, say, Yamnaya people moved in the first place. The size of westward and eastward migrations and ways in which each passage unfolded over several centuries also remain mysterious. Perhaps most crucially, sets of genes shared by distant populations can’t explain how ancient cultures and languages changed over time.
Despite the uncertainties, the Yamnaya’s wandering DNA makes one thing clear, says Eske Willerslev, an evolutionary geneticist at the University of Copenhagen. “Bronze Age pastoralists moved long distances for a long time and had an important impact on European and central Asian civilizations.” Willerslev directed one of the 2015 Yamnaya investigations. A team led by Harvard Medical School geneticist David Reich conducted the other study. Efforts to flesh out how ancient herders became movers and shakers in the rise of civilization are now in full swing, as evidenced by a range of new papers.
Jo Bowyer Chartered Physiotherapist Registered Osteopath. "Out beyond ideas of wrongdoing and rightdoing,there is a field. I'll meet you there." Rumi
We process personal data about users of our site, through the use of cookies and other technologies, to deliver our services, personalize advertising, and to analyze site activity. We may share certain information about our users with our advertising and analytics partners. For additional details, refer to our Privacy Policy.
By clicking "I AGREE" below, you agree to our Privacy Policy and our personal data processing and cookie practices as described therein. You also acknowledge that this forum may be hosted outside your country and you consent to the collection, storage, and processing of your data in the country where this forum is hosted.
Tweet
Comment