HOMININS, APES AND MONKEYS
human an gorilla skeletons Hominins are defined as creatures that stand upright and walk and run primarily on two legs, while apes are creatures that hunch over and, although capable of walking on two legs, prefer to use their arms when moving on the ground. Before the mid 2000s, scientists often referred to hominins as hominids. Hominids are all modern and extinct great apes: gorillas, chimps, orangutans and humans, and their immediate ancestors. Not gibbons. Hominins are any species of early human that is more closely related to humans than chimpanzees, including modern humans themselves.
What distinguishes an ape from a monkey is the fact that apes don’t have a tail. Humans are apes. They are just as hairy as other apes, but their hair is shorter and finer. Apes are regarded as more intelligent than monkeys. They have rapid eye movement and may dream. They can recognize themselves in a mirror while monkeys think they are confronted with another monkey. Apes and humans are the only creatures that have spindle cells — large cigar-shaped cells neurons linked with emotion, problem-solving, a moral sense and a feeling of free will — in their brains.
Research by geneticists in the mid 2000s determined that the human genome and chimpanzees are only different by 1.23 percent. The one small percentage difference encompasses 35 million individual chemical changes accumulated over the 5 million to 7 million years during which the species evolved apart. Put another way humans and chimpanzees share 98.77 percent of the same genetic material. Not everyone likes this figure. A study in Japan however that 15 percent of genes of humans and chimpanzees are different.
Websites and Resources on Hominins and Human Origins: Smithsonian Human Origins Program humanorigins.si.edu ; Institute of Human Origins iho.asu.edu ; Becoming Human University of Arizona site becominghuman.org ; Hall of Human Origins American Museum of Natural History amnh.org/exhibitions ; The Bradshaw Foundation bradshawfoundation.com ; Britannica Human Evolution britannica.com ; Human Evolution handprint.com ; University of California Museum of Anthropology ucmp.berkeley.edu; John Hawks' Anthropology Weblog johnhawks.net/ ; New Scientist: Human Evolution newscientist.com/article-topic/human-evolution
Timeline of Monkey, Ape and Hominin Development
Scientists have found fossils of 5,000 individual hominins as far back as 4.4 million years, perhaps 7 million years. The earliest hominins, the genus Australopethecus, possessed long arms, short legs, a large small brain and a large face. These creatures would appear to us today as more ape-like than human-like. So far the earliest hominins species have been discovered only in eastern, northern and south Africa. Scientists describe Africa as the "cradle of mankind" because all of the oldest hominin remains have been found there.
About 25 million years ago the line that would eventually lead to apes split from the old world monkeys. Between 20 million and 14 million years ago orangutans split off from the other “great apes,” chimpanzees, gorillas and humans. Between 14 million and 5 million years ago numerous species of early apes spread across Asia, Europe and Africa
Archicebus achilles
✦395 million years ago: Tetrapods evolve from lobe-finned fish, as animals move on to the land.
✦ 55 million years ago: Archicebus achilles living in what is now China.
✦ 47 million years ago: Darwinius masillae living in Messel pit area of what is now modern Germany.
✦Between 8 million and 4 million years ago: First the gorillas, and then chimpanzees and bonobos split off from the evolutionary lineage that led to humans.
✦ 3.8 million years ago: Australopithecus afarensis, an ape-like hominin living in Africa. Most famous fossil is Lucy.
✦ 300,000 years ago: Homo sapiens evolves in Africa.
✦Between 125,000 and 60,000 years ago: Homo sapiens leaves Africa. [Source: Alok Jha, The Guardian, June 5, 2013]
Early attempts to plot the course of human evolution tried to present nice neat linear models with one species leading directly to another. The more discoveries that were made the less the neat models became. Modern models of human evolution look like groups of trees with lots of entangled branches — some that lead to dead ends and others that continue on and interconnect to other branches. In the old days many thought who studied early man were regarded as “lumpers” because they tended to lump discoveries into group. In recent years they have taken a backseat too “splitters,” who shy away from grouping new discoveries and instead often define them as new, separate species.
New discoveries have also debunked theories that human evolution was marked by a series of nice, neat progressions and advancements. Sometimes new discoveries dated to a certain period seem more primitive than older finds. Some features in one species appear and then disappear and then re-emerged in later species, making the features insignificant as some sort of milestone. Bernard Wood of George Washington University told Newsweek, “Similar traits evolved more than once, which means you can’t use them as gold-plated evidence that one fossil is descended from another or that having an advanced trait means a fossil was a direct ancestor of modern humans.”
Earliest Known Primate: A Tiny, Insect-Eating Creature from China
The oldest primate fossils date to around 55 million years ago. There is circumstantial evidence based on mathematics and probability that they lived as far back as 80 million years which would have made them contemporaries of the dinosaurs.
Archicebus achilles, a tiny-insect-eating creature that lived 55 million years ago present-day China, is regarded as the ancestor of all monkeys, apes and humans Alok Jha wrote in The Guardian: “A tiny animal with slender limbs, a long tail and weighing in at no more than 30 grams, has become the earliest known primate in the fossil record. Archicebus achilles lived on a humid, tropical lake shore 55 million years ago in what is now China and is the ancestor of all modern tarsiers, monkeys, apes and humans. Scientists found the fossil, whose name translates as "ancient monkey", in the Hubei province of China about a decade ago but it hasn't received detailed analysis until now. [Source: Alok Jha, The Guardian, June 5, 2013 |=|]
“About seven centimeters long, Archicebus lived in the trees and its small, pointed teeth are evidence that its diet consisted of insects. The fossil's large eye sockets indicate a creature with good vision and, according to scientists, it probably hunted during daytime. Xijun Ni of the Chinese Academy of Sciences, who led the study of the fossil, described the animal as having a very long tail, slender limbs, a round face and feet capable of grasping. "Maybe it would also have had colours and it would have preyed on insects," he said. A full description of the fossil is published in the latest edition of Nature. |=|
“The analysis shows that the fossil had a mixture of features found in modern-day tarsiers, an ancient group of primates that is now restricted to the islands of South East Asia, and others found in anthropoids, the lineage through which monkeys, apes and humans later evolved. Whereas Archicebus's foot looks like that of a modern-day marmoset, for example, the heel bone looks more like those seen in the earliest fossil anthropoids. |=|
“Chris Beard of the Carnegie Museum of Natural History in Pittsburgh, a co-author on the Nature paper, added that, because the animal was so small and "active metabolically, it was probably quite a frenetic animal, you could even think anxious. Very agile in the trees, climbing and leaping around in the canopy. The world it inhabited along that lake shore in central China was amazing – hot, humid, very tropical." |=| “Archicebus was alive during a period of intense global warming known as the palaeocene-eocene thermal maximum, a time when palm trees would have been growing as far north as Alaska. Dr Christophe Soligo, a biological anthropologist at University College London, said the discovery of the fossil was a significant contribution to scientific knowledge of early primate evolution. "It does not only contribute new fossil material to a period for which very little is preserved, but it contributes a new specimen that is astonishingly complete for its age." |=|
“To study the delicate skeleton without damaging it, scientists created a high-resolution, digital reconstruction of the fossil using x-rays at the European Synchrotron Radiation Facility in Grenoble, France. Dr Jerry Hooker, a palaeontologist at the Natural History Museum in London, said: "Most mammal fossils, including those of primates, are fragmentary, usually consisting of isolated teeth or jaws, sometimes also other skeletal elements, and we have learned a lot from these. However, to have a 50 percent complete articulated skeleton of a primitive primate is much more instructive in terms of estimating lifestyle and relationships."” |=|
Ida: the 47-Million-Year-old “Missing Link”
In a review of the book: “The Link: Uncovering Our Earliest Ancestor” by Colin Tudge with Josh Young, Guy Gugliotta wrote in the Washington Post: “In 2006, paleontologist Jorn Hurum, of the University of Oslo's Natural History Museum, was shown the remains of a small, (22 inches) juvenile female primate from the oil shales of the Messel Pit, near Frankfurt, Germany, one of Europe's most famous fossil beds. The fossil had been discovered in 1983 by a private collector who wanted to sell it. His asking price was $1 million. Hurum was immediately smitten, for the find "represented a once-in-a-lifetime experience for any paleontologist." The museum bought it. [Source: Guy Gugliotta, Washington Post, June 28, 2009 ||=||]
“Hurum assembled a team of experts to analyze and describe the fossil, a process that has thus far taken three years. The team concluded that "Ida," so named in honor of Hurum's daughter, shared characteristics with evolutionary lineages that led both to modern lemurs and to the anthropoids — including humans. "In other words," Tudge writes, "Ida appears to be an in-between species, or one of the long-sought missing links in evolution." ||=||
“In their peer-reviewed paperin the online scientific journal PLoS One, Hurum and his team say Ida "could represent a stem group from which later anthropoid primates evolved, but we are not advocating this here." Tudge describes Ida's world, a tropical forest with a volcanic lake that one day belched a gigantic bubble of toxic gas that asphyxiated this small creature and plunged it into the mud for all eternity. ||=||
"The Link" isn't just about a monkey fossil. It's about paleontology and paleontologists, warts and all. As noted, Hurum bought his fossil at an annual fair in Hamburg, Germany, from a collector, and paid big bucks for it. Many scientists regard such transactions as mortal sin, for they can encourage looting and the destruction of fossil sites, damaging ancient contexts that can never be reconstructed. In Tudge's telling, Hurum carefully selects his research team, knowing that it must be not only expert but also beyond professional reproach, because colleagues will relentlessly scrutinize its work. He needs a primate specialist. He needs a tooth expert. He needs somebody who knows the Messel Pit.” ||=||
Books: “The Link: Uncovering Our Earliest Ancestor” by Colin Tudge with Josh Young (Little, Brown, 2009); “Origins: The Story of the Emergence of Humans and Humanity in Africa” edited by Geoffrey Blundell (Double Storey, 2006)
Development of Early Primates, Lemurs and Monkeys
Alok Jha wrote in The Guardian: ““The Archicebus skeleton is about 7 million years older than the oldest currently known fossil primate skeletons, including Darwinius massilae from Messel in Germany, an extremely well-preserved fossil was that reported by scientists in 2009. Better known as Ida, it was originally thought to be a direct ancestor of the primate lineage leading to monkeys, apes and humans – but further analysis suggests Ida is closer to early lemurs. [Source: Alok Jha, The Guardian, June 5, 2013 |=|]
“The discovery of Archicebus in China lends weight to the idea that the first and most pivotal steps in primate evolution, including the beginnings of anthropoid evolution, almost certainly took place in Asia, rather than Africa. "The evidence that early primate revolution was restricted to Asia is becoming more compelling by the day," said Beard. "It consists of two different types of data – the first is genomic. If we sequence the DNA of living primates and other mammals, we find out that the closest living relatives of primates are animals like tree shrews and flying lemurs and these are animals that only live today in Asia, specifically south-eastern Asia." |=|
“The second strand of evidence comes from the fossil record. There is some evidence of primates living in Africa about 55 million years ago, but the knowledge is patchy and comes only from a few bones and teeth. "Africa at this point in time was an island continent with a very endemic and specialised mammal fauna that in some ways resembles the modern mammal fauna of Australia in the sense that it's strange – it's not like what we see on other continents," said Beard. |=|
“At some point, the descendants of Archicebus split into the lineages that would later evolve into tarsiers and anthropoids. The latter would then have made their journey to Africa and, millions of years later, evolved into humans. "We do know that early anthropoids and early fossil relatives were somehow able to make it to Africa by the end of the Eocene, roughly 38 million years ago is our best estimate," said Beard. "We still don't know how these Asian anthropoids, which had been evolving in Asia for around 20 million years by this time, made it to Africa. But we know it could not have been easy." |=|
“At the time, Africa was an island and had yet to collide with the south western side of the continent of Asia. The early primates somehow had to cross open water in order to colonise Africa. "It couldn't have been easy but they did and, after that, obviously the story changed and Africa became a pivotal centre for anthropoid evolution," said Beard.
Early Primates and Apes
One of the earliest primates so far discovered is a 33 million year old arboreal animal nicknamed the "dawn ape" found in the Egypt's Faiyum Depression. This fruit-eating creature weighed about eight pounds (three kilograms) and had a lemur-like nose, monkey-like limbs and the same number of teeth (32) as apes and modern man.
Fossils of 20.6 million-year-old common ancestor of man and apes was unearthed in Uganda in the 1960s. The animals was about 1.2 meters tall and weighed between 40 and 50 kilograms and was described by thought as a "cautious climber."
In 2011, Reuters reported: Ugandan and French scientists had discovered a fossil of a skull of a tree-climbing ape from about 20 million years ago in Uganda's Karamoja region. The scientists discovered the remains in July while looking for fossils in the remnants of an extinct volcano in Karamoja, a semi-arid region in Uganda's northeastern corner. "This is the first time that the complete skull of an ape of this age has been found. It is a highly important fossil," Martin Pickford, a paleontologist from the College de France in Paris, said. [Source: Elias Biryabarema, Reuters, August 2, 2011]
Pickford said preliminary studies of the fossil showed that the tree-climbing herbivore, roughly 10-years-old when it died, had a head the size of a chimpanzee's but a brain the size of a baboon's, a bigger ape. Bridgette Senut, a professor at the Musee National d'Histoire Naturelle, said that the remains would be taken to Paris to be x-rayed and documented before being returned to Uganda. Uganda's junior minister for tourism, wildlife and heritage said the skull was a remote cousin of the Homininea Fossil Ape.
See Gigantopithecus Under PRIMATES — MONKEYS, MACAQUES, GIBBONS, AND LORISES—IN CHINA factsanddetails.com
Human Ancestors Hunted by Raptors and Wolf-Size Creodonts
creodant
Early humans may have evolved as prey to animals such a s large birds and carnivorous mammals, rather than as predators, remains of primates that lived before our human ancestors suggest. Jennifer Viegas wrote in discoverynews: “The discovery of multiple de-fleshed, chomped and gnawed bones from the extinct primates, which lived 16 to 20 million years ago on Rusinga Island, Kenya, was announced today at the Society of Vertebrate Paleontology’s 70th Anniversary Meeting in Pittsburgh. [Source: by Jennifer Viegas, discoverynews, October 12, 2010 ^||^]
“At least one of the devoured primates, an early ape called Proconsul, is thought to have been an ancestor to both modern humans and chimpanzees. It, and other primates on the island, were also apparently good eats for numerous predators. “I have observed multiple tooth pits and probable beak marks on these fossil primates, which are direct evidence for creodonts and raptors consuming these primates,” researcher Kirsten Jenkins told Discovery News. ^||^
“Creodonts were ancient carnivorous mammals that filled a niche similar to that of modern carnivores, but are unrelated to today’s meat eaters, she explained. The Rusinga Island creodonts that fed on our primate ancestors were likely wolf-sized. “There is one site on Rusinga Island with multiple Proconsul individuals all together and these are covered in tooth pits,” added Jenkins, a University of Minnesota anthropologist. “This kind of site was likely a creodont den or location where prey could be easily acquired.” ^||^
“Analysis of tooth pits, de-fleshing marks, bone breakage patterns, gnawing and other damage to the primate bones indicate that raptors were also hunting down these distant relatives of humans. “Primatologists have observed large raptors taking monkeys from trees,” Jenkins said. “When a raptor approaches a group of monkeys, those monkeys will make alarm calls to warn their group and attempt to retreat to lower branches. The primates on Rusinga had monkey-like postcrania and likely had very similar locomotor behavior.” Jenkins is not certain what selective pressures predators placed on these very early primate ancestors to humans, but she said they “can affect behavior, group structure, body size and ontogeny (the life cycle of a single organism).”^||^
“Robert Sussman, professor of physical anthropology at Washington University in St. Louis, has long argued that primates, including early humans, evolved not as hunters but as prey of many predators, including wild dogs and cats, hyenas, eagles and crocodiles. “Despite popular theories posed in research papers and popular literature, early man was not an aggressive killer,” said Sussman, author of the book “Man the Hunted: Primates, Predators and Human Evolution.” “Our intelligence, cooperation and many other features we have as modern humans developed from our attempts to out-smart the predator. He added that the idea of man as hunter “developed from a basic Judeo-Christian ideology of man being inherently evil, aggressive and a natural killer.” “In fact, when you really examine the fossil and living non-human primate evidence, that is just not the case,” he explained. ^||^
Apes Become More Human-Like
Baboon-size apes that lived in East Africa about 15 million years ago may have spent most of its time on the ground. This finding is based on the hand, finger arm and shoulder bones from a ape called Equatorious found in 1993 in the Tugen Hills of north central Kenya. A fossil of an ape that lived 13 million years ago in Spain has been described as a common ancestor to all apes and hominins and led some to theorize that the ancestral ape that spawned gorillas, chimpanzees and human came to Africa from Eurasia.
Between 11 million and 8 million years ago gorillas split off from chimpanzees and humans. In 2007 an Ethiopian and Japanese team of scientists announced in a Nature article that they had found a 10-million-year-old ape 170 kilometers south of Addis Ababa in Ethiopia that was very similar to a gorilla that provided some grounds for pushing back the date of the split between humans and apes. The discovery also supported the theory that the apes that spawn humans originated in Africa.
Rudapithecus was the name given to a 10-million-year-old great ape unearthed in Hungary. Some have called the ape the closest fossil hunters gave come to finding a common ancestor of humans and African apes. Named after the village of Hungarian Rudabanya, near where it was found, it had a body and brain about the size of a chimpanzee. Its long arms and curved fingers indicate it spent a lot of time hanging from the branches of trees. Modest-size molars and thin tooth enamel suggested it ate soft fruits.
Split Between Apes and Hominins
Based on DNA evidence in blood proteins, molecular biologists guess that the hominin line split off from the ape line between 5 and 8 million years ago, a period of time in which little is known about apes or hominins and there is little data in the fossil record.
The generally accepted assumption is that gorillas and ancestors of chimpanzees and humans split around 6 million to 8 million years ago. Some DNA evidence seems to indicate that hominins and chimpanzees split between 5.5 million and 6.5 million years ago.
Calculations made by geneticists based on the differences between genomes indicates that the chimpanzees and hominins diverged no later than 6.3 million years ago and probably earlier than 5.4 million years ago. This finding raises questions about fossils that are more than five million years old — namely “Sahelanthropus tchadensis” and “Orrorin tugenensis — that are claimed to belong to hominin species.
A team led by David Reich of the Broad Institute in Cambridge, Massachusetts has suggested that one explanations for the discrepancy between the fossil record (that says the oldest hominin are 7 million years old) and genetic evidence (which dates hominin and chimpanzee divergence at around 5.3 million years ago) is that chimpanzees and early hominin might have had sex with each other and interbred. That could also explain why some early hominins have strange mixture of human and chimpanzee traits. One should not jump to too many conclusions though as there is still a lot of uncertainty over dating and inferences made from small quantities of fossils.
Last Common Ancestor of Humans and Chimpanzees
The last common ancestor of humans and he apes such as chimpanzees, gorillas, orangutans and gibbons lived during the Miocene epoch (23 million to 5 million years ago). At this point it is a theoretical construct as no fossils of it have been found. Scientists believe the last common ancestor of humans and chimpanzees had shoulders similar to those of modern African apes, a finding supports the theory that early humans moved away from life in trees gradually. Charles Q. Choi wrote in Live Science: “The human lineage diverged from that of chimpanzees, humanity's closest living relative, about 6 million or 7 million years ago. Knowing the characteristics of the last common ancestor of humans and chimps would shed light on how the anatomy and behavior of both lineages evolved over time, "but fossils from that time are rare," said lead author of the new study Nathan Young, an evolutionary biologist at the University of California, San Francisco. [Source: Charles Q. Choi, Live Science, September 8, 2015 +]
“There are currently at least two competing scenarios for what the last common ancestor might have looked like. One suggests that similarities seen in modern African apes, such as in chimps and gorillas, were inherited from the last common ancestor, meaning that modern African apes may reflect what the last common ancestor was like. "A lot of people use chimpanzees as a model for the last common ancestor," Young told Live Science. The other scenario suggests these similarities instead evolved independently in modern African apes, and that the last common ancestor may have possessed more-primitive traits than those seen in modern African apes. For instance, instead of knuckle-walking on the ground like chimps and gorillas do, the last common ancestor may have swung and hung from tree branches like orangutans, which are Asian apes. Humans aren't the only species that have evolved and changed over time — chimpanzees and gorillas have evolved and changed over time, too, so looking at their modern forms for insights into what the last common ancestor was like could be misleading in a lot of ways," Young said. +\
“The ancestral state of the shoulder is key to understanding human evolution, because the shoulder is linked to many important shifts in behavior in the human lineage. Shoulder evolution could help show when early human ancestors began using tools more, spent reduced time in trees and learned to throw weapons. However, the human shoulder possesses a unique combination of features that makes it difficult to reconstruct the body part's history. For instance, while humans are most closely related to knuckle-walking chimps, in some respects the human shoulder is more similar in shape to that of tree-dwelling orangutans. +\
“To see what the shoulder of the last common ancestor might have looked like, researchers generated 3D shoulder models from museum specimens of modern humans, chimps, bonobos, gorillas, orangutans, gibbons and monkeys. The scientists compared these data with 3D models that other scientists previously generated of ancient, extinct relatives of modern humans, such as Australopithecus afarensis, Australopithecus sediba, Homo ergaster and Neanderthals. +\ Australopithecines such as Australopithecus afarensis and Australopithecus sediba are the leading candidates for direct ancestors of humans. "Recent data from the australopithecines helped us now test different models of human evolution," Young said. +\
“The scientists found the strongest model showed the human shoulder gradually evolving from an African apelike form to its modern state. "We found australopithecines were perfect intermediate forms between African apes and modern humans," Young said. This finding suggests the human lineage experienced a long, gradual shift out of the trees and increased reliance on tools as it became more terrestrial, he said. "These results pretty much confirm that the simplest explanation for how the human shoulder evolved is the most likely one," Young said. The scientists detailed their findings online Sept. 7, 2015 in the journal Proceedings of the National Academy of Sciences.” +\
Imaging What the Last Common Ancestor Between Humans and Apes Looked Like
We don’t know what our last common ancestor (LCA) looked liked. Determining its size and what its skull, brain, legs, arms and fingers looked like is all educated guesswork, mainly based on looking at the closest equivalents alive — gorillas, chimpanzees and gibbons. Charles Q. Choi wrote in Live Science: One big unknown is the LCA's size, said Christopher Gilbert, a paleoanthropologist at Hunter College of City University of New York, told Live Science. That's because ape fossils from the period during which the LCA lived are scarce, a 2017 study in the journal Nature noted. Early or "stem" apes span a large range of body sizes, from small gibbon-size species to larger primates approaching gorilla-size, making it difficult to pin down the heft of the LCA without a better understanding of the evolutionary relationships and history of these species, said Gilbert, who co-authored the Nature study. [Source: Charles Q. Choi, Live Science, July 4, 2023]
SahelanthropusThe LCA was likely a four-legged animal, current evidence suggests. Fossils indicate that stem apes were capable of climbing vertically and of having suspensory behavior, just as modern humans can use their arms to hang from tree branches. However, unlike all living apes, which prefer to live hanging below or among tree branches, at least some stem apes were not specialized for suspensory behavior, lacking adaptations such as long, highly curved fingers and toes, and highly mobile wrists, shoulder and hip joints. This implies the LCA may not have been specialized for suspension either, Gilbert said. Some researchers have occasionally speculated "that maybe the LCA was a biped," moving on two legs like a human,Thomas Cody Prang, a paleoanthropologist at Washington University in St. Louis, told Live Science. However, because "the LCA was a quadruped, like other primates, "it's likely that it didn't walk on two legs but rather used all fours.
Stem apes displayed a range of head shapes. Some had skulls like gibbons with short faces while others had longer faces resembling primitive apes and Old World monkeys, such as baboons (genus Papio) and macaques (genus Macaca), Gilbert said. Still, "we know with near-certainty that the brain size of the LCA was smaller than a human's brain size," Prang said. Because it was a quadruped, the head wouldn't have sat on top of the body like a biped's does, but positioned more forward like a gorilla or chimp.
The arms and legs of early apes often are not well-preserved in the fossil record. Still, "the upper limbs of early hominins [humans and our close relatives and ancestors] appear to be large and heavily built, which is associated with forelimb-dominated locomotion — that is, climbing and suspension," Prang said. As for the legs, early hominins appear to have had short hind limbs, more like great apes — gorillas (Gorilla gorilla and Gorilla beringei) , chimpanzees (Pan troglodytes), orangutans (genus Pongo) and bonobos (Pan paniscus) — than humans, he noted. In essence, early hominins appear to be built for tree canopies, not the open savanna.
In terms of the hand, in a 2021 study in the journal Science Advances, Prang and his colleagues analyzed Ardipithecus, a 4.4 million-year-old early fossil hominin, and found its hand "was most similar to chimpanzees and bonobos among all living humans, apes, and monkeys." This in turn, may suggest the LCA had long, curved finger bones.
Humans, chimps, gorillas and bonobos all walk with their heels touching the ground, suggesting the LCA did the same, Prang said. This form of movement is also often linked with other traits seen in living African apes — gorillas, chimps and bonobos — such as using knuckles to help in walking, and evolutionary adaptations to climb vertically. "All of the traits that we can reasonably study suggest that the earliest hominins, and therefore probably the LCA, were characterized by these same components of this adaptive package," Prang said. "The LCA was neither a gorilla nor a chimpanzee, but it was likely most similar to gorillas and chimpanzees among all known primates." In all, the appearance of the LCA "is still all quite contentious," Gilbert said. Filling in the picture will require new fossil discoveries.
Earliest Hominins
Sahelanthropus tchadensisThe first human-like traits to appear in the hominin fossil record are bipedal walking and smaller, blunt canines. The brains sizes of the earliest hominins was not all that different from apes such as orangutans, chimpanzees and gorillas.
Changes from an ape-like anatomy to a hominoid one become apparent in fossils from the late Miocene Period (10.4 million to 5 million years ago) in Africa. Some hominoid species from this period have traits that typical of humans but are not seen in the other living apes, leading paleoanthropologists to infer that these fossils represent early members of the hominin lineage. [Source: Nature]
The oldest fossils that have been widely accepted at least of possibly belonging to hominin species are 7-million-year-old Sahelanthropus tchadensis and 6-million-year-old Orrorin tugenensis. Many though think these fossils belong to ape species not hominin ones. (See Early Hominins)
See Separate Article: EARLIEST HOMININS AND OLDEST HUMAN ANCESTORS: ARDIPITHECUS (ARDI), SAHELANTHROPUS AND ORRORIN factsanddetails.com
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Text Sources: National Geographic, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Nature, Scientific American. Live Science, Discover magazine, Discovery News, Times of London, Natural History magazine, Archaeology magazine, The New Yorker, Time, Newsweek, BBC, The Guardian, Reuters, AP, AFP and various books and other publications.
Last updated April 2024