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Descent of Man In this lecture, beginners can familiarize themselves with basic information and terms used to describe the evolution of humanity beginning with the origin of primates through the comings and goings of Genus Homo. |
Earliest Fossil Evidence Of Differences Between Sexes
Posted: Thursday, January 23, 2003
Source: University Of Toronto
Prehistoric Tusks Point To Earliest Fossil Evidence Of Differences Between Sexes
The large tusks of an animal that roamed Earth before the dinosaurs may provide the earliest evidence yet of male-female distinctions in land animals that existed millions of years ago, say University of Toronto scientists.
Robert Reisz, a biology professor at the University of Toronto at Mississauga, and his team have found convincing evidence of sexual dimorphism - different physical traits between the sexes of the same species - in their study of fossils from between 252 to 260 million years ago. They believe that the male Diictodon, a herbivorous barrel-shaped creature, had two large tusks extending down from the upper jaw. The tusks, Reisz says, were used as weapons, possibly for ritualistic or physical combat.
"Our findings give very clear evidence of complex social behaviour," Reisz says. "To see this kind of behaviour [physical combat] early in the history of the group that eventually gave rise to mammals is really quite startling."
Reisz's study, which is featured on the cover of the January issue of the Proceedings of the Royal Society of London B, was based on detailed studies of nearly a hundred skeletons unearthed in South Africa over the last two decades.
Diictodon appeared during the Late Permian Period of the Paleozoic Era, at least 30 million years before dinosaurs existed. It was part of a group of animals described as mammal-like reptiles and was an evolutionary relative of the animals that evolved into mammals. Diictodon, which was covered in scales and measured about one metre in length, was a burrowing herbivore with a beaked skull and short tail.
In its investigation, the team was able to rule out other uses for the tusks, Reisz says. The tusks were not used for feeding because the females did not have them nor were they used for digging because the ends did not show signs of wear. It appears the tusks became longer, wider and thicker as the animals aged and extended well below the jaw line; those lost, possibly in combat, were never replaced, Reisz says. "All these factors are very strong indicators of armament."
Reisz says these findings go beyond the standard skeletal descriptions that accompany research on fossils. "This is a wonderful opportunity to study the biology of animals that lived so long ago. Rather than just simply looking at them and describing them, we can do more with their lifestyle, with their feeding habits, and with their general biology than just looking at their skeletons would suggest."
Along with Reisz, the study involved Corwin Sullivan, now a graduate student at Harvard University, and Dr. Roger M.H. Smith of the South African Museum in Cape Town, South Africa. The research was funded by the Natural Sciences and Engineering Council of Canada and by the American Museum of Natural History.
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The University of Toronto, Canada's leading research university with 60,000 students, is celebrating its 175th anniversary. On March 15, 1827, King's College - precursor to the University of Toronto - was granted its royal charter by King George IV. The university now comprises 31 divisions, colleges and faculties on three campuses, including 14 professional faculties, numerous research centres and Canada's largest university library system - the fifth largest research library in North America.
The original news release can be found here
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Posted: Thursday, January 23, 2003
by Mark Henderson
http://www.timesonline.co.uk/article/0,,3-552033,00.html
Fossils found in China of a winged and feathered dinosaur indicate that birds evolved from a line of tree-dwelling raptors
A SPECTACULAR set of fossils belonging to a winged and feathered dinosaur has been unearthed in China, providing one of the final missing links in the evolution of birds.
Microraptor gui, a new species that lived about 128 million years ago, used four feathered limbs to glide from tree to tree like a flying squirrel - a "halfway" means of flight by which the first birds probably took to the skies.
The small predator, which grew to about two and half feet long, will settle a long-running debate about how the cousins of Tyrannosaurus rex and Velociraptor evolved into modern birds.
It is the first truly intermediate fossil that is part-dinosaur and part-bird. Its unique physical traits indicate that birds emerged from a line of small, tree-dwelling dinosaurs, which first learnt to glide as they hunted, or were being hunted, and progressed to flight.
This would rule out the theory that flight originated among ground-based feathered dinosaurs. Only last week, a study of modern partridges suggested a way in which such creatures might have learnt to take off, by flapping their forelimbs for thrust and traction.
Microraptor gui belongs to a group of theropod or predatory dinosaurs known as the basal dromaeosaurids, which most experts accept as the ancestors of birds. It had feathers arranged aerodynamically on its fore and hind limbs, and its long, streamlined tail.
This combination of wings and a tail would have been ideal for gliding, instead of running on the ground, where the leg feathers would have got in the way.
Xing Xu, of the Institute of Vertebrate Palaeontology and Palaeoanthropology in Beijing, who led the research team, said that the forelimb and leg feathers would have made a perfect aerofoil, similar to a bat’s stretched web of skin.
"These features together suggest that basal dromaeosaurids probably could glide, representing an intermediate stage between the flightless non-avian theropods and the volant (flying) avians."
The research suggested that the new species first learnt to glide, "by taking advantage of gravity, before flapping flight was acquired".
Six specimens of the creature, which is named after the distinguished Chinese palaeontologist Gu Zhiwei, have been discovered in Liaoning Province in northeastern China, and details are published today in the journal Nature.
Over the past five years, dozens of feathered dinosaur remains have been found in Liaoning, suggesting that theropod dinosaurs were the ancestors of birds - as was first suggested by Thomas Henry Huxley as early as 1868. Previous finds, however, have belonged to feathered but flightless creatures such as "fuzzy raptor", one of the centrepieces of the "Dino-Birds" exhibition on display at the Natural History Museum in London.
Microraptor gui appears to confirm the work of the naturalist William Beebe, who in 1915 proposed that the first flying birds were gliders, equipped with wing feathers on both arms and legs.
Richard Prum, an evolutionary biologist at the University of Kansas, said that the new fossil "looks as if it could have glided straight out of Beebe’s notebooks. The discovery provides striking support for the arboreal-gliding hypothesis of the origin of bird flight."
Microraptor gui and the other dinobirds of Liaoning lived between 128 million and 122 million years ago, making them much younger than Archaeopteryx, which at 147 million years is the most ancient bird known to science.
The discoveries carry huge evolutionary significance because Archaeopteryx is a close relation, and, though older, is likely to have developed from a feathered dromaeosaur similar to Microraptor.
"It looks confusing that this is later in time than Archaeopteryx, but that does not make this discovery any less stunning," said Angela Milner, associate keeper of palaeontology at the Natural History Museum.
"It is just an accident of preservation." The evidence now points overwhelmingly to a treetop origin for modern birds, Dr Milner said. "We are looking at small, agile dinosaurs with very curved claws, adapted for climbing trees," she said. "It looks as if feathers evolved first for insulation."
The evolutionary trail
Microraptor gui: 128-124 million years ago; c 2 ft long. Newly-discovered "missing link" between dinosaurs and birds that used four feathered limbs to glide from tree to tree.
Archaeopteryx: 147 million years ago. First known bird - toothed beak, feathered wings capable of powered flight. Probably evolved from creature similar to Microraptor gui.
Dromaeosaurs: Feathered dinosaurs living 130-120 million years ago. Mostly flightless predators; used feathers for insulation. Include Microraptor gui and "fuzzy raptor" fossil on display at Natural History Museum.
Sinornithosaurus millenii: 124 million years ago. Dromaeosaur covered in downy feathers. First complete skeleton of a feathered dinosaur discovered.
Protarchaeopteryx and Caudipteryx: 130-120 million years ago. Feathered, flightless dino-birds discovered in Liaoning province in 1997. Had fans of tail-feathers.
Archaeoraptor liaoningensis: Elaborate fake, announced in 1999 as the "missing link" between dinosaurs and birds. Turned out to be two fossils stuck together - the bottom half of a dromaeosaur, and the top half of a primitive bird, Yanornis martini.
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Flap over dino flight origins Posted: Thursday, January 16, 2003
Reproduced from BBC, Thursday, 16 January, 2003
http://news.bbc.co.uk/1/hi/sci/tech/2664541.stm
A new theory of how dinosaurs learned to fly has emerged.
According to a US scientist, flight may have evolved in two-legged dinosaurs that flapped their feathered fore-limbs to climb slopes.
They eventually developed true wings and became flying birds, says Kenneth Dial of the University of Montana.
The idea is based on a study of the habits of modern flightless birds, which beat their wings to scurry up hills and get away from predators.
It turns out that the physics of this sort of flapping motion is different from that of aerial flight.
Foot traction
Professor Dial says it helps push the birds' feet against the slope, thus improving traction - in the same way that spoilers work on a racing car.
He came to this conclusion by studying partridges running up hills and measuring their speed.
Even chicks with downy fluff were better at getting up steep slopes than those whose flight feathers had been trimmed or removed.
By modifying these wing movements, birds or their ancestors - the dinosaurs - may have been able to launch themselves into the air.
Fossils show that some dinosaurs had feathered fore-limbs but were unable to fly - something that has puzzled palaeontologists.
Rival theories
Professor Dial believes that what he calls wing-assisted incline running was first seen in prehistoric times.
But the idea is likely to ruffle a few feathers. There has been heated debate about how dinosaurs learned to fly.
One camp believes ground-dwellers grew feathers that helped them run faster and eventually become airborne.
A more recent school of thought favours the idea that flight arose from the tree down - as small meat-eating dinosaurs leapt from branch-to-branch in the canopies.
Dr Angela Milner, a dinosaur expert at London's Natural History Museum, says the latest theory is a "third way".
"The work adds a new dimension to the whole debate on how flight evolved," she told BBC News Online.
"A predator escape mechanism using wing-assisted incline running fits with what we see in the fossils."
The research is published in the journal Science. Professor Dial's theory is featured in an on-going exhibition, Dino Birds, the feathered dinosaurs of China, at London's Natural History Museum.
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"Dark Energy" Dominates The Universe Posted: Friday, January 3, 2003
Source: Dartmouth College
HANOVER, NH - A Dartmouth researcher is building a case for a "dark energy"-dominated universe. Dark energy, the mysterious energy with unusual anti-gravitational properties, has been the subject of great debate among cosmologists.
Brian Chaboyer, Assistant Professor of Physics and Astronomy at Dartmouth, with his collaborator Lawrence Krauss, Professor of Physics and Astronomy at Case Western Reserve University, have reported their finding in the January 3, 2003, issue of Science. Combining their calculations of the ages of the oldest stars with measurements of the expansion rate and geometry of the universe lead them to conclude that dark energy dominates the energy density of the universe.
"This finding provides strong support for a universe which is dominated by a kind of energy we've never directly observed," says Chaboyer. "Observations of distant supernova have suggested for a few years that dark energy dominates the universe, and our finding provides independent evidence that the universe is dominated by this type of energy we do not understand."
The researchers came to this conclusion as they were refining their calculations for the age of globular clusters, which are groups of about 100,000 or more stars found in the outskirts of the Milky Way, our galaxy. Because this age (about 12 billion years old) is inconsistent with the expansion age for a flat universe (only about 9 billion years old), Krauss and Chaboyer came to the conclusion that the universe is expanding more quickly now than it did in the past.
The only explanation, according to Chaboyer and Krauss, for an accelerating universe is that the energy content of a vacuum is non-zero with a negative pressure, in other words, dark energy. This negative pressure of the vacuum grows in importance as the universe expands and causes the expansion to accelerate.
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Read more about dark energy: http://www.dartmouth.edu/~news/releases/may01/universe.html
Read more about calculating the age of stars: http://www.dartmouth.edu/~news/releases/may01/stars.html
The original news release can be found here.
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Ape culture hints at earlier evolution Posted: Thursday, January 2, 2003
From: BBC & The New York Times
http://news.bbc.co.uk/2/hi/science/nature/2622101.stm
Decades of orang-utan watching has led scientists to believe that some of the animals have developed their own culture.
Using leaves and sticks to gather food and building sun covers for nests, are just some of the ways that orang-utans make their lives easier in the wild.
An international research project into the behaviour of these giant apes suggests there is extensive social contact between the animals.
The discovery could also help scientists understand how human culture developed.
Raspberries
Researchers investigated six sites in Borneo and Sumatra for wild orang-utan behaviours.
They looked for signs of cultural activity, which would show the animals communicated closely with each other.
Culture can be described in many different ways, but the basic elements include labels, signals, skills and symbols.
The scientists found some orang-utan populations use leaves as protective gloves or napkins, swat insects with leafy branches and make "raspberry" sounds when going to sleep.
Some orangutans use tools like leaves to gather food or water.
Some of the groups even play sport. During "snag-riding," the animals ride falling dead trees, grabbing vegetation before the tree hits the ground.
Human origins
The findings could shed light on how early human behaviour evolved.
The complex behaviour of orangutans suggests human culture started to develop 14 million years ago, much earlier than thought.
At this time the ancestors of chimps and orangutans diverged.
Professor Carel van Schaik from Duke University in Durham led one of the teams behind the study.
He said: "Culture requires more than just a mother-infant bond, but also extensive social contact, and orangutans are at the low end of the sociability spectrum.
"While we were by no means certain that we would come up with any evidence for cultural variability, we ultimately identified 24 behaviours that likely represent cultural variants."
Each population behaves differently, suggesting that the orangutans do indeed learn from their close companions.
Professor Van Schaik warned though that political unrest and habitat destruction could prevent further studies.
"Some of the areas included in this study have already been lost to illegal logging.
"Even if somehow you could restore the forest and the animals, just as with human cultures, once a culture is gone, it's gone."
The research is published in the journal Science.
Scientists Say Orangutans Can Exhibit 'Culture'
http://www.nytimes.com/2003/01/03/science/03APE.html
Orangutans, those red-haired knuckle-dragging apes, are loping today into the upper echelons of the primate hierarchy. According to research reported in the journal Science, they exhibit what was until very recently considered a uniquely human attribute, culture.
Drawing on years of research and thousands of hours of observations from six sites in the wild, an international team of scientists found evidence that orangutan groups differ across a spectrum from bedtime rituals to eating habits to sexual practices, patterns of behavior learned from being around others in a group that scientists call culture.
Other researchers said four years ago that chimpanzees also exhibited widespread cultural differences, for example, in how they groom, hunt, eat and so on. Scientists say that the new work suggests that the two remaining great-ape species, gorillas and bonobos, are highly likely to have culture, as well, and that great-ape culture dates from at least the group's origin 14 million years ago.
The finding has been of particular interest, as orangutans have long been thought to be loners, leaving little possibility for creating culture. Yet researchers found that at one site all orangutans gave a Bronx cheer before going to sleep, while at other sites the ritual was absent. In some forests, orangutans had a characteristic way to hunt and kill a beast known as the slow loris or extracting seeds from the stinging fruit of the Neesia tree. In other forests with the loris and Neesia, orangutans never took those meals. And although in two forests, orangutans enjoyed masturbation using sticks, elsewhere such behavior was unheard of.
As is typical when scientists seek to award attributes of Homo sapiens to other creatures, there has been heated reaction. Some experts say that although quite unlikely, orangutans may behave differently at different sites because of undetected habitat differences. Some scientists also object in principle to using the freighted term "culture," which has long been used to denote something peculiarly human.
Further research on orangutan culture may be difficult, however, because the species as a whole is threatened, as people steadily encroach on its habitats.
But other experts said great-ape cultures were the tip of the iceberg.
"In the coming 20 years, we will have a host of studies on culture in all sorts of animals," said Dr. Frans B. M. de Waal, a primatologist at Emory University, pointing to studies that suggest cultural differences among rats, birds and even fish. "We will not think of culture as a monolithic thing, but a concept that includes songbirds, the great apes and human culture."
The orangutan study grew out of a workshop that gathered researchers who had worked for years in isolation at remote sites on Borneo and Sumatra, the sole places orangutans are found in the wild.
"You know your own animals, and all of them do particular things," said Dr. Carel P. van Schaik, a biological anthropologist at Duke University and the lead author on the paper. "So you think all orangutans do these things. Nobody thought there'd be so much variation between the sites."
Dr. van Schaik said there was no evidence of ecological or genetic differences that would lead to such differences in behavior. In addition, sites where orangutans spent more time together reported more of the widespread behaviors, as would be expected with behaviors that can be spread through association. In addition, the closer together sites were, the more shared behaviors.
But Dr. Bennett G. Galef Jr., an animal behaviorist at McMaster University, cautioned that it could be difficult to decipher what causes differences in behavior among populations in the wild. In a classic example, chimps are known to use very different methods for extracting ants from nests in eastern and western Africa. But in a recent study, researchers reported finding a new group of chimps that use either method, depending on how aggressive the ant that they are hunting is. Dr. Galef said the finding suggested that even this cultural divide might have a hidden ecological explanation as simple as the difference in what kinds of ants were available to chimps in different areas.
Most work has relied on observing animals in the wild. Dr. Galef said the only way to answer definitively many of the important questions would be through field experiments. Unfortunately, researchers say, some of the newly uncovered cultures have probably been destroyed.
Dr. van Schaik said the home of the Bronx cheer and the loris hunting on Sumatra had been devastated by a wave of illegal logging despite its being in a park. Another long-term study site on Borneo has been devastated by civil war and is too dangerous to visit.
Even if he was able to return, he said, "probably all the orangutans we knew there are gone."
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'Dark Energy' Dominates The Universe Posted: Thursday, January 2, 2003
Source: Dartmouth College
HANOVER, NH - A Dartmouth researcher is building a case for a "dark energy"-dominated universe. Dark energy, the mysterious energy with unusual anti-gravitational properties, has been the subject of great debate among cosmologists.
Brian Chaboyer, Assistant Professor of Physics and Astronomy at Dartmouth, with his collaborator Lawrence Krauss, Professor of Physics and Astronomy at Case Western Reserve University, have reported their finding in the January 3, 2003, issue of Science. Combining their calculations of the ages of the oldest stars with measurements of the expansion rate and geometry of the universe lead them to conclude that dark energy dominates the energy density of the universe.
"This finding provides strong support for a universe which is dominated by a kind of energy we've never directly observed," says Chaboyer. "Observations of distant supernova have suggested for a few years that dark energy dominates the universe, and our finding provides independent evidence that the universe is dominated by this type of energy we do not understand."
The researchers came to this conclusion as they were refining their calculations for the age of globular clusters, which are groups of about 100,000 or more stars found in the outskirts of the Milky Way, our galaxy. Because this age (about 12 billion years old) is inconsistent with the expansion age for a flat universe (only about 9 billion years old), Krauss and Chaboyer came to the conclusion that the universe is expanding more quickly now than it did in the past.
The only explanation, according to Chaboyer and Krauss, for an accelerating universe is that the energy content of a vacuum is non-zero with a negative pressure, in other words, dark energy. This negative pressure of the vacuum grows in importance as the universe expands and causes the expansion to accelerate.
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Read more about dark energy:
www.dartmouth.edu/~news/releases/may01/universe.html
Read more about calculating the age of stars:
www.dartmouth.edu/~news/releases/may01/stars.html
The original news release can be found at:
www.dartmouth.edu/~news/releases/jan03/dark-energy.shtml
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