The human wave: people may have evolved fluidly, with lots of interbreeding.Release a drop of red food coloring into a glass filled with water. Watch the drop slowly spread until it imbues the water with a rosy tint 1. TINT - Interpreted version of JOVIAL.
[Sammet 1969, p. 528].
2. tint - hue . Then, add a drop of blue coloring and observe the boundaries of purple expand. According to according to
1. As stated or indicated by; on the authority of: according to historians.
2. In keeping with: according to instructions.
3. Vinayak Eswaran, this process, known as diffusion, reflects how, over the past 200,000 years, people evolved to have the relatively thin bones, small jaws, and other distinctive aspects of their current physical form.
A mechanical engineer at the Indian Institute The Indian Institute in central Oxford, England is located at the north end of Catte Street on the corner with Holywell Street and faching down Broad Street from the east. of Technology in Kanpur, Eswaran is an unlikely emissary EMISSARY. One who is sent from one power or government into another nation for the purpose of spreading false rumors and to cause alarm. He differs from a spy. (q.v.) of insights into human evolution. He primarily studies how chemicals and heat move through fluids. In his field, diffusion refers to a process in which molecules of a chemical in a fluid randomly bump into other molecules. These jostled particles follow erratic paths, taking what researchers call random walks. As a result, a chemical initially concentrated in one part of an apparently still fluid moves to other areas.
Eswaran says that in 1997, he was "powerfully struck" by the notion that diffusion provides a way to explain a major anthropological mystery--the rise of anatomically modern humans. After testing a number of mathematical models of diffusion's role in human evolution, Eswaran identified a promising one.
He dubbed his hypothesis "the diffusion wave out of Africa." This model melds diffusion to an idea proposed by University of Chicago geneticist ge·net·i·cist
A specialist in genetics.
a specialist in genetics.
geneticist Sewall Wright Sewall Green Wright ForMemRS (December 21, 1889 – March 3, 1988) was an American geneticist known for his influential work on evolutionary theory and also for his work on path analysis. With R. A. Fisher and J.B.S. Haldane, he was a founder of theoretical population genetics. more than 70 years ago. Wright held that, in a population of species composed of many small groups that rarely interact, individuals in some groups evolve combinations of genes that boost their survival rates. Sets of these advantageous genes slowly spread throughout the population as individuals from different groups occasionally mate.
In Eswaran's scenario, an advantageous combination of genes spread among ancient hunter-gatherer groups that inhabited overlapping regions of eastern Africa. It's likely that this genetic package fostered body features such as a relatively small face, thin skull bones, and, in females, a wide pelvis--all being traits that improved the chance that mothers and babies survive childbirth, Eswaran asserts.
For the most part, Eswaran emphasizes, people evolved through the spread of that critical gene combination that eased childbirth, not by amassing a patchwork of individually beneficial genes, as researchers have typically assumed. "This explains the unique and rapid evolution of humans, compared with our closest evolutionary cousins, the apes," he says.
The beneficial suite of genes flowed from one group to the next as if a wave. Around 100,000 years ago, the genetic diffusion wave of modern Homo sapiens Homo sapiens
(Latin; “wise man”)
Species to which all modern human beings belong. The oldest known fossil remains date to c. 120,000 years ago—or much earlier (c. with the critical gene mix edged into Asia, advancing no more than a few miles each generation. As tens of thousands of years passed, modern humans washed over Asia and Europe as well as into the far reaches of Africa, occasionally interbreeding interbreeding
crossbreeding, as between half-breds. with Homo erectus Homo erectus (hō`mō ērĕk`təs), extinct hominid living between 1.6 million and 250,000 years ago. Homo erectus is thought to have evolved in Africa from H. habilis, the first member of the genus Homo. and perhaps other now-extinct Homo species. Our genetic evolution occurred through a process that was closer to a random walk across the Old World than to a series of planned migrations, Eswaran says. If the diffusion-wave model holds up, it goes a long way toward ironing out apparent conflicts in different aspects of current human genetic makeup, he proposes.
One vein of research--typically cited in support of relatively recent human origins solely in Africa--examines mitochondrial DNA Mitochondrial DNA (mtDNA) is the DNA located in organelles called mitochondria. Most other DNA present in eukaryotic organisms is found in the cell nucleus. Nuclear and mitochondrial DNA are thought to be of separate evolutionary origin, with the mtDNA being derived from the . This material is inherited solely from one's mother and exhibits far more mutations in modern Africans than it does in Asians and Europeans. Accounting for the estimated rate at which mitochondrial-DNA mutations accumulate, the patterns are consistent with a diffusion wave of H. sapiens sa·pi·ens
Of, relating to, or characteristic of Homo sapiens.
[Latin sapi moving out of Africa at least 130,000 years ago.
On the other hand, analyses of DNA DNA: see nucleic acid.
or deoxyribonucleic acid
One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes. from the cell's nucleus indicate that human genetic heritage in Asia is far older than it is in Africa, making it appear that modern humans originated in Asia.
Eswaran's solution: Evidence of ancient nuclear DNA Nuclear DNA , nuclear deoxyribonucleic acid (nDNA), is DNA contained within a nucleus of eukaryotic organisms. In most cases it encodes more of the genome than the mitochondrial DNA and is passed sexually rather than matrilineally. sequences in Asian populations, much of it dating to between 1 million and 500,000 years ago, reflects the genetic contributions of species such as H. erectus to modern humanity as populations diffused across the Old World. Since mutations accumulate much more slowly in nuclear DNA than they do in mitochondrial DNA, nuclear DNA lineages go back further in time.
"While modern humans first emerged in Africa, we now carry a substantial genetic inheritance that had its origins in non-African Homo species," Eswaran says.
The Indian researcher's model is one of several new attempts to understand people today as genetic products of two or more ancient humanlike populations that interbred in·ter·breed
v. in·ter·bred , in·ter·breed·ing, in·ter·breeds
1. To breed with another kind or species; hybridize.
2. at least occasionally. These approaches put a new spin on the long-standing debate over the nature of human evolution.
DIFFUSION PROFUSION Until a few years ago, anthropologist Henry Harpending Henry C. Harpending (1944- ) is an anthropologist and population geneticist at the University of Utah, where he is a Distinguished Professor. Harpending has broken new ground in anthropology and human biology interpreting genetic and morphometric variation within and between human of the University of Utah The University of Utah (also The U or the U of U or the UU), located in Salt Lake City, is the flagship public research university in the state of Utah, and one of 10 institutions that make up the Utah System of Higher Education. in Salt Lake City championed the recent-African-origin theory of modern humans. In that influential scenario, a single population evolved in Africa roughly 200,000 years ago and eventually migrated throughout the world, replacing H. erectus, European and Middle Eastern Neandertals, and any other Homo species encountered.
Harpending changed his mind upon seeing Eswaran's explanation of the diffusion-wave theory in 2002. That model "explains available genetic and fossil data better than anything we have had until now," Harpending said at that time.
Eswaran and Harpending, with Utah's Alan R. Rogers, have now conducted computer simulations of how humanity's diffusion wave advanced from Africa across Asia. Their findings appear in the July Journal of Human Evolution.
A simulated diffusion wave of beneficial genes that begins in Africa requires substantial interbreeding with native Asian Homo populations to yield the patterns of genetic variation on those continents observed today, the scientists conclude.
Their findings indicate that it would take roughly 80,000 years for a highly advantageous combination of genes in 100 fertile adults living in eastern Africa to spread to eastern Asia through diffusion, if there were 100 comparably sized H. erectus groups spaced evenly across that geographic expanse. As this simulated slice of evolution plays out, interbreeding incorporates pieces of H. erectus nuclear DNA into that of modern humans, the researchers suggest.
The diffusion wave that the team modeled hit some geographic roadblocks, Eswaran notes. It stopped upon reaching the Indian Ocean Indian Ocean, third largest ocean, c.28,350,000 sq mi (73,427,000 sq km), extending from S Asia to Antarctica and from E Africa to SE Australia; it is c.4,000 mi (6,400 km) wide at the equator. It constitutes about 20% of the world's total ocean area. . Instead of succumbing to the genetic wave of modern humans, Australia, for example, was settled by seafaring H. erectus groups around 60,000 years ago, followed by migrations of early humans from Asia as late as 15,000 years ago, in his view. A brief period of interbreeding then preceded the ascendance as·cen·dance also as·cen·dence
Noun 1. ascendance - the state that exists when one person or group has power over another; "her apparent dominance of her husband was really her attempt to make him pay of modern humans down under, possibly explaining why fossils of Australian H. sapiens and Asian H. erectus look so much alike.
EVOLUTIONARY SUBDIVISIONS Eswaran's approach has received the warmest welcome from researchers who already suspected that interbreeding contributed to human evolution. Most such scientists advocate multiregional evolution, in which African, Asian, and European Homo populations migrated among continents and interbred enough to foster the simultaneous evolution of modern H. sapiens in each region.
Some multiregional theorists, such as anthropologist Milford Wolpoff of the University of Michigan (body, education) University of Michigan - A large cosmopolitan university in the Midwest USA. Over 50000 students are enrolled at the University of Michigan's three campuses. The students come from 50 states and over 100 foreign countries. in Ann Arbor Ann Arbor, city (1990 pop. 109,592), seat of Washtenaw co., S Mich., on the Huron River; inc. 1851. It is a research and educational center, with a large number of government and industrial research and development firms, many in high-technology fields such as , propose that the fossil record over the past 2 million years consists only of various forms of ancient H. sapiens that intermingled enough to produce people today. In Wolpoff's view, genetic diffusion could have occurred solely within a single, anatomically diverse species. He calls the diffusion-wave model a "particularly insightful description of how multiregional evolution might be expected to work."
Anthropologist John H. Relethford of the State University of New York (body) State University of New York - (SUNY) The public university system of New York State, USA, with campuses throughout the state. in Oneonta says that Eswaran's approach has much in common with a "mostly-out-of-Africa" scenario that Relethford proposed in 2001. He hypothesized that close to 200,000 years ago, large African populations of H. sapiens began to interbreed interbreed
to breed between animal or plant species, breeds, families. with small numbers of H. erectus in Asia and Neandertals in Europe.
Populations outside Africa gradually assumed the basic genetic characteristics of the African immigrants, in Relethford's opinion. Survival-enhancing genes in the immigrants would have hastened that process but wouldn't have been essential, he adds.
Eswaran's diffusion model looks promising, even as other candidates for explaining human evolution are emerging, notes geneticist Michael F. Hammer of the University of Arizona (body, education) University of Arizona - The University was founded in 1885 as a Land Grant institution with a three-fold mission of teaching, research and public service. in Tucson.
As described in a report slated to appear in Genetics, he and his colleagues analyzed patterns of mutations along extensive, comparable chunks of X chromosomes in 42 men from different parts of the world. Two of 10 Africans carried a distinctive DNA sequence DNA sequence Genetics The precise order of bases–A,T,G,C–in a segment of DNA, gene, chromosome, or an entire genome. See Base pair, Base sequence analysis, Chromosome, Gene, Genome. with numerous mutations that apparently took more than 1 million years to evolve. Other Africans in the sample carried a different signature DNA sequence that was nearly as old. Distinctive Asian and European sequences with smaller numbers of mutations also appeared, some overlapping with others.
According to Hammer, the X chromosome data best fit a scenario in which African H. sapiens split into two major populations, possibly close to 1 million years ago. The two populations then evolved in isolation for hundreds of thousands of years before interbreeding, perhaps in Africa, with other Homo species.
It's hard to know whether genes critical for modern humans then spread through diffusion as one group interbred with the next or via migrations of various groups back and forth across the landscape, Hammer says.
Another new scenario of human evolution emphasizes the latter possibility. Separate groups of ancient H. sapiens, not yet exhibiting all the anatomical traits of people today, constantly moved through overlapping home territories for much of the past 1 million years, sometimes mating with each other and forming new groups and at other times dying out, suggests anthropologist Rosalind M. Harding of the University of Oxford in England. Her proposal is based on a model developed by Harvard University Harvard University, mainly at Cambridge, Mass., including Harvard College, the oldest American college. Harvard College
Harvard College, originally for men, was founded in 1636 with a grant from the General Court of the Massachusetts Bay Colony. geneticist John Wakeley.
BACK TO AFRICA Even if a previously unsuspected number of ancient populations contributed to modern human evolution, as Eswaran and some others now propose, people may still have relatively recent African roots, says geneticist Laurent Excoffier of the University of Bern The University of Bern is a university in the Swiss capital of Bern. It was founded in 1834. As one of the German-speaking universities in Switzerland its official name is Universität Bern, although it is frequently referred to in the French form, Université de Berne. in Switzerland.
Excoffier suspects that modern humans evolved from one of several ancient H. sapiens populations in Africa around 200,000 years ago. A small number of those fledgling people then migrated to Asia. As the population expanded, separate groups formed in different areas. Colonization of Europe by a group from western Asia occurred toward the end of the Stone Age.
This model requires no diffusion, and sporadic interbreeding between species was irrelevant on an evolutionary scale. Some ancestral genes could have been carried out of Africa, while being lost within Africa. That would explain why Asians carry much older stretches of DNA than Africans do.
Interbreeding between the African emigrants and the Homo species that they encountered was so rare that it had no lingering impact on modern DNA, Excoffier argues. One new analysis indicates that, at most, only 120 successful matings between Neandertal mothers and H. sapiens fathers contributed to the current makeup of mitochondrial DNA, which includes no gene found in ancient samples of Neandertal mitochondrial DNA.
That rate of interbreeding is so low that it "strongly suggests almost complete sterility between Neandertal females and modern human males," Excoffier and his Swiss colleague Mathias Currat concluded in the December 2004 PloS Biology PLoS Biology is a scientific journal covering the full spectrum of the biological sciences that began operation on October 13, 2003. It was the first journal of the Public Library of Science (PLoS) a non-profit organization which releases scientific content under open . So far, there's no way to estimate the extent of interbreeding between H. sapiens mothers and Neandertal fathers.
Anthropologist Christopher Stringer of the British Museum British Museum, the national repository in London for treasures in science and art. Located in the Bloomsbury section of the city, it has departments of antiquities, prints and drawings, coins and medals, and ethnography. in London agrees with Excoffier and Currat. From Stringer's perspective, the fossil record supports an African origin between 200,000 and 100,000 years ago, "although there must have been very many human expansions and contractions."
Anthropologist Jeffrey Schwartz Jeffrey Schwartz is a research professor at the University of California in Los Angeles (UCLA) who is a major proponent of the idea that human will, intention or consciousness is nonmaterialistic and dualistic, possibly even being a "mental force" similar to that of gravity. of the University of Pittsburgh, also a supporter of recent African origins, takes a dim view of evolutionary reconstructions based on DNA. From Eswaran to Excoffier, researchers make assumptions about how DNA works that are implausible in light of discoveries in developmental genetics Developmental genetics
The study of how genes control development. Advances in the field have emphasized the degree of conservation of the genes controlling development throughout evolution. , Schwartz says.
DNA differences offer a hazy view of evolution, at best, in his opinion. Individual DNA sequences can play many different roles in developmental pathways. Evolutionary processes may primarily influence species-specific growth processes that unfold once gene activity is completed, Schwartz argues.
"Until we rethink basic assumptions about DNA, the prospects for understanding human evolution with genetics look pretty bleak," he says.
Eswaran, however, remains upbeat about the prospects for his model of our genetic origins. It's attracted a lot of interest in a short time, and he's ready to ride the diffusion wave as far as it goes.
Julia Lindsay (Member): The need for a new religion 6/26/2009 4:38 AM
The importance of a random variable and how it is relative is this. lets take a interaction between 2 people. one feels rejected by the other which causes them to feel hurt which then might cause a negative action in say they speak of this person in a negative way, you could think so what, sticks and stones right, but you would be wrong, this single variable will be in the big equation in the one of the factors in the demise of human beings.We know how dinosaurs died out, its the same principle, a combination of things wiped them out, we know one thing can offset another so on and so on, now with humans these same things could happen but we will have the extra factor of the damage they we cause to ourselves and the planet, now one thing could of been different, and dinosaurs could of been still here today, now what im saying is that we might be able to change one of the factors that contribute to us.We need to change the way we think,The problems with humans is that they cant seem to get passed their self. their self comes first always,and they dont seem to know it,or not care, as far as being evolved we are very young, now if we forgot about our self and only and always thought of the what was best for everyone overall, big picture and small,for the greater good%2