Courtesy wikimediaThe Smithsonian Institute will open a new exhibition hall tomorrow (March 17, 2010), the David H. Koch Hall of Human Origins (this opening coincides with the institute’s 100-year anniversary). The 15,000-square-foot hall will focus on what it means to be human, examining how our defining characteristics emerged over time. One cool thing about the new exhibition (in addition to…everything) is the highlight (in the form of bronze statues) of a-typical hominid species. There’s a statue of Homo heidelbergensis, Paranthropus boisei, and even Homo floresiensis (the “hobbit” species). Now, I know what you’re thinking, “What?! Where’s the Australopithecus africanus?!!” Well, it’s not in this exhibition (at least not in the form of a shiny effigy). The reason for this is to emphasize that our ancestry is not a straight line (as A. africanus might imply because it is a possible direct ancestor of Homo sapiens). Instead, our lineage is much less tidy; there’s species overlap, some species die off… the diagrams are messy. The David H. Koch Hall of Human Origins is trying to get at the fact that we Homo sapiens are just another iteration in our branch-laden tree, not the pinnacle of evolutionary development. I think that’s a great point to remind people of.
Other features of the exhibition include forensically reconstructed life-sized faces of some of our ancestors, 75 skull reproductions, key events in humanity’s evolution (environmental changes, behavioral innovations, etc.), a human family tree, and virtual tours of important research sites. I haven’t had the chance to visit it yet, but the American Museum of Natural History in New York also has a relatively new human origins exhibition. I think it’s exciting that more and more museums are taking on this topic. In the past museums have shied away from it for fear of stirring up controversy. The Milwaukee Public Museum, for example has an exhibit about evolution- it’s on a tiny wall in a dark corner…but at least they have one. It’s important for museums to present scientific research, and the exciting exploration of human evolution is no exception. So if you’re in the D.C. area, be sure to check out the new Smithsonian Hall of Human Origins.
After some three and a half billion years of life’s evolution on this planet – and after almost two million years since people recognizable as human first walked its surface – a new human burst upon the scene, apparently unannounced.
It was us.
Until then our ancestors had shared the planet with other human species. But soon there was only us, possessors of something that gave us unprecedented power over our environment and everything else alive. That something was – is – the Human Spark.
What is the nature of human uniqueness? Where did the Human Spark ignite, and when? And perhaps most tantalizingly, why?
In a three-part series to be broadcast on PBS in 2010, Alan Alda takes these questions personally, visiting with dozens of scientists on three continents, and participating directly in many experiments – including the detailed examination of his own brain.
Have scientists finally found a Rock n' Roll gene? Not really, but researchers have made some interesting discoveries about the genetic basis of birdsongs, which are passed down from generation to generation through social interaction much in the same way that you or I learn to talk, sing, dance, cook or create. When the authors of a new study on the transmission of birdsong behaviors in zebra finches isolated and raised birds in silence, they expected them to sing off-key. While the mating songs of these 'untrained' birds were much less appealing to the opposite sex, after several generations the untrained lineage produced offspring that were able to sing just like those in the wild. You can listen to the experiment here. This news has left researchers wondering where birdsongs originally began, and to what extent cultural behaviors are hard wired. While zebra finches and humans are only very distant relatives, researchers think we may be able to learn about human culture and genetics from studies like these. After all, as the authors point out, our human cultures (including language, music and a whole host of other things) are very different, but they all share common elements across the globe. In the end, these cultural underpinnings may turn out to be part of our biology.
scientists discovered the skeleton of a fossil human on the Indonesian island of Flores. Fully-grown but only 3 feet tall, the fossil set off a storm of controversy. Was it a new species of ancient human? Was it a pygmy – a member of a group genetically disposed to shortness? Was it an individual suffering from some rare disease?
Early reports claimed that it was a dwarf form of Homo erectus, an ancestor of modern humans. Animals will sometimes evolve pygmy forms when trapped on an island with limited resources. But some scientists disputed that theory. They noted that the skeleon is only 18,000 years old, whereas H. erectus went extinct at least 50,000 years ago. Also, the skeleton was surrounded by sophisticated tools. These scientists held that the skeleton represented an individual Homo sapiens who suffered from microcephaly, a rare disease which gives people small heads and sometimes small bodies.
But a recent re-examination of the fossil
supports a different theory. Scientists at the University of Florida argue that the original interpretation was right. The structure of the brain, as imprinted on the skull, is different from H. erectus, microcephalics, and even from us. They believe this fossil represents a new species of ancient human, one more closely related to H. sapiens than to H. erectus.
This raises the possibility that, in the not-too-distant past, two separate species of humans lived on the Earth. (And if you count Neanderthals, which went extinct around 24,000 years ago, there would have been three.)
Scientists will continue to examine the fossils, and try to develop theories that best explain all the evidence.
Did Neanderthals, the stocky, muscular human relatives that dominated Europe until 30,000 years ago, have the ability to communicate through language? And if so, did any of their chat sessions ever lead to dating and possibly mating with us, their not-so-distant cousins?
DNA extracted from the thigh bone of a caveman who lived 38,000 years ago in Croatia may supply scientists with the answers to these and other questions.
Two studies, one in Germany, the other in California, have reported new and exciting techniques for compiling the entire genome for Neanderthals, modern humans closest and most recent evolutionary link. Their research results, reported in the journals Nature and Science, respectively, convey they have demonstrated independently that it is now possible to recover the Neanderthal genome. Just a few years ago, the idea of doing this kind of sequencing was considered hopeless.
Dr. Svante Paabo who led one project at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany said that one million units of the estimated 3.2 billion units of Neanderthal DNA have already been mapped.
What has made this possible is a new DNA sequencing machine developed by a Branford, Connecticut company called 454 Life Sciences. The new sampler uses firefly light to sort through and catalogue vast amounts of fragmented DNA.
Dr. Paabo also shared some of his precious sample of Neanderthal DNA with Edward M. Rubin of the Joint Genome Institute in Walnut Creek, California. Using a different method, Rubin’s team identified 62,250 units of Neanderthal DNA.
Richard G. Klein, a Stanford University paleoanthropologist not involved in the studies, found the results “monumental.” He added that the full Neanderthal genome would resolve many longstanding questions about Neanderthals and their connection to modern humans, including physical and behavioral differences.
Of particular interest is whether Neanderthals could speak and had developed a language. The FOXP2 gene is thought to be one of the last evolving components leading to language development and has shown significant change since human-chimpanzee split occurred about six million years ago. If the Neanderthal genome is fully retrieved, and the FOXP2 gene more resembles the chimp version, then the thinking is that language development is less likely.
Dr. Paabo’s team has estimated the establishing Neanderthal population size to be about 3,000 individuals, while Dr. Rubin’s team reports that human and Neanderthal genomes are at least 99.5 percent identical. However, both research teams think it unlikely the two species interbred but the idea cannot be completely ruled out.
The extraction of readable DNA poses problems for scientists. The samples are often contaminated by bacterial DNA that attacked the remains when they were fresh or other human DNA left from curators or scientists handling the specimens.
On top of that, DNA begins to quickly degrade into short fragments after death making it tricky to locate a sample that has somehow survived. Dr. Paabo searched through museum collections all across Europe before finally finding one that satisfied his stringent criteria. It was a small bone from a cave in Croatia that had languished in a box of insignificant and relatively little-handled fossils. Only about 6 percent of the DNA present was Neanderthal, but with the new sequencing machine it should be more than enough to retrieve the specie’s gene sequence.
With 1 million units of Neanderthal DNA already mapped, Dr. Paabo estimates the rest should be completed in about two years.
SOURCES and MORE INFO:
New genetic studies theorize that humans and chimpanzees may have split genetically much later in their evolution than previously thought - as recent as 6.3 million years ago - and that the initial split was followed by phases of interbreeding and hybridization before the two species headed off on their own evolutionary paths.
The results come out of a long and arduous examination of genetic codes of humans, chimps, gorillas and other apes.
“We found that the population structure that existed around the time of human-chimpanzee speciation was unlike any modern ape population,” said David Reich, of the Broad Institute of Harvard and the Massachusetts Institute of Technology. “Something very unusual happened at the time of speciation.”
If the theory is correct, it would mean that present-day humans descended from a chimp-human hybrid, an idea that goes against the current view that hybrid branches tend to lead to dead ends.
The findings, which appeared in the journal Nature, also suggest that some of the oldest “proto-human” fossils may not be human ancestors at all, but may have come from the branch of non-hybrids that died out.
By tracing the history of the X chromosome, scientists determined that after the initial split, females of each species could have bred successfully with males of the other, thereby creating hybrids. Male offspring of this union would probably been sterile, but female offspring would be fertile and could have continued to breed with fertile males of either species, thus creating further hybridization.
Scientists were able to trace the evolutionary history of the X chromosome by comparing human and chimpanzee genes. The genetic evolutionary clock indicated that the male X chromosome found in present day humans wasn’t as old as it should have been had it been passed down from ancestors that came before the initial human-chimpanzee split.
Stories of chimp-human hybrids have been around for centuries, but never confirmed. One recent example from the 1970’s was a performing chimp named Oliver, who was long-rumored to be the product of human and chimpanzee interbreeding. However, DNA studies done at the University of Chicago proved him to be pure chimpanzee.