View Full Version : Number of ancestral human species: a molecular perspective.

Tuesday, September 16th, 2003, 06:07 PM
Homo. 2003;53(3):201-24.

Number of ancestral human species: a molecular perspective.

Curnoe D, Thorne A.

Department of Archaeology and Natural History, Research School of Pacific and Asian Studies, Australian National University, Canberra ACT 0200, Australia. d.curnoe@unsw.edu.au

Despite the remarkable developments in molecular biology over the past three decades, anthropological genetics has had only limited impact on systematics in human evolution. Genetics offers the opportunity to objectively test taxonomies based on morphology and may be used to supplement conventional approaches to hominid systematics. Our analyses, examining chromosomes and 46 estimates of genetic distance, indicate there may have been only around 4 species on the direct line to modern humans and 5 species in total. This contrasts with current taxonomies recognising up to 23 species. The genetic proximity of humans and chimpanzees has been used to suggest these species are congeneric. Our analysis of genetic distances between them is consistent with this proposal. It is time that chimpanzees, living humans and all fossil humans be classified in Homo. The creation of new genera can no longer be a solution to the complexities of fossil morphologies. Published genetic distances between common chimpanzees and bonobos, along with evidence for interbreeding, suggest they should be assigned to a single species. The short distance between humans and chimpanzees also places a strict limit on the number of possible evolutionary 'side branches' that might be recognised on the human lineage. All fossil taxa were genetically very close to each other and likely to have been below congeneric genetic distances seen for many mammals. Our estimates of genetic divergence suggest that periods of around 2 million years are required to produce sufficient genetic distance to represent speciation. Therefore, Neanderthals and so-called H. erectus were genetically so close to contemporary H. sapiens they were unlikely to have been separate species. Thus, it is likely there was only one species of human (H. sapiens) for most of the last 2 million years. We estimate the divergence time of H. sapiens from 16 genetic distances to be around 1.7 Ma which is consistent with evidence for the earliest migration out of Africa. These findings call into question the mitochondrial "African Eve" hypothesis based on a far more recent origin for H. sapiens and show that humans did not go through a bottleneck in their recent evolutionary history. Given the large offset in evolutionary rates of molecules and morphology seen in human evolution, Homo species are likely to be characterised by high levels of morphological variation and low levels of genetic variability. Thus, molecular data suggest the limits for intraspecific morphological variation used by many palaeoanthropologists have been set too low. The role of phenotypic plasticity has been greatly underestimated in human evolution. We call into question the use of mtDNA for studies of human evolution. This DNA is under strong selection, which violates the assumption of selective neutrality. This issue should be addressed by geneticists, including a reassessment of its use for molecular clocks. There is a need for greater cooperation between palaeoanthropologists and anthropological geneticists to better understand human evolution and to bring palaeoanthropology into the mainstream of evolutionary biology.

Dr. Solar Wolff
Wednesday, October 1st, 2003, 07:04 AM
Has anyone heard anything about the DNA testing done on the new gorilla species found in Africa? This ape is taller than a gorilla and walks upright. Evidently, this gorilla's foot most resembled a lowland gorilla but the initial mitochondrional DNA test linked it most closely with the chimp. But unlike the chimp, it builds ground nests. Locals call it the "Lion eater" becasue it is so tall. DNA tests were supposed to have been done (the story broke late last Spring).

Returning to genetic distance used in systemics, its about time. As a geneticist told me once, anthropologists are not educated enough to do anthropology, they are educated to follow along when real progress is made by more biologically oriented scientists. Unfortuately, genes are such an abstraction as compared with skulls that people tend to fall back on the familiar. After all, we all can recognize the skulls of famous finds just by sight. We can't do that with genetic maps. But DNA doesn't lie (except in the case of the O.J. Simpson jury). Interesting things have been learned recently concerning Canius. While there is great phenotypic variation in wild and domestic dogs it was found that the genetic variation found within wolves fits inside the total variation of domestic dogs. They also calculated a gentic clock for the wolf - dog seperation and it is over 100,000 years old. If dogs came from the asiatic wolf as is usually said, then perhaps Homo erectus domesticated the dog. Without using DNA evidence, we have thought the dog-wolf seperation to be about 14,000 years old and wolves and dogs to be seperate species. Big difference. Now we know that they are all one species. Wolves and humans had a wide geographic distribution so there are similarities. New evidence suggests that the grey wolf of Europe and Asia is different to some grey wolves of the far western and eastern USA and to the red wolf of the deep south. At the same time there are the Eur-Asian wolves in the New World, mostly in the center of the continent, running all the way to Mexico. Further, there is an extict wolf, the Canius diruswhose morphology differed from grey wolves in teeth, jaw and crainial cavity. We don't know its place yet. Somehow, this all sounds like Homo, especially Homo sapiens and Homo neanderthalensis.

Wednesday, October 1st, 2003, 01:46 PM
Thanks for citing this perspective, volksdeutsche.

To be honest, I have always been sceptical of these brave claims of mtDNA genetic clocks, and to say that all living humans shared a common ancestor 100,000 years ago, is now called into question by some. I welcome this, and hope it would encourage subsequent and further investigation. It also shows you how easily some people accept the first claims that *some* geneticists make, in this case namely the 100,000 year claim. The whole world was virtually running with this idea, but now it seems it may be way off the mark.



Wednesday, October 1st, 2003, 02:33 PM
Here's that story from CNN about that new ape...

Seeking answers to big 'mystery ape'
Clues to new ape species?
By Marsha Walton
Saturday, August 9, 2003 Posted: 11:05 AM EDT (1505 GMT)

A skull belonging to a 'mystery ape,' on the left, is placed next to a chimpazee skull for comparison. Researchers say the mystery ape is much more 'flat-faced' and substantially bigger.


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We cannot rule out the possibility that it is a new species of ape, or a new subspecies or some form of hybrid.
-- Duane Rumbaugh, professor at Georgia State University

(CNN) -- From a remote region in the heart of Africa to a genetics lab at the Omaha Zoo, scientists are trying to find out if they have a new big ape on their hands.

"It doesn't look much like a gorilla, it doesn't look like a chimpanzee," said primatologist Shelly Williams, who captured a bit of video of the female mystery ape with a baby.

Pictures of the rare ape are scarce. Wildlife photographer Karl Amman, who was first to spot the mysterious mammals a few years ago, said the animal has feet that are about two inches bigger than the average gorilla and is more flat-faced than other apes. Its behavior also sets it apart from other apes, researchers say.

The mystery ape often sleeps in big ground nests. Chimpanzees, for example, usually nest in trees to stay away from predators. And the mystery apes hoot when the moon rises and sets, something chimps don't do for fear of attracting lions and hyenas, Williams said.

So what could this animal be?

"We cannot rule out the possibility that it is a new species of ape, or a new subspecies or some form of hybrid," said Duane Rumbaugh, a professor at Georgia State University.

"Discovering any new primate is a huge thing, a new ape would be incredible, " said Ed Louis, conservation geneticist at the Henry Doorly Zoo in Omaha, Nebraska.

Common ancestor
Chimpanzees, bonobos (also known as pygmy chimps), and gorillas are all members of the ape family. Present-day apes and humans had a common ancestor in the distant past -- perhaps 6 million years ago, scientists say.

But Amman found some evidence and plenty of local legend to suggest another type of big ape also may call Africa home. The forest in the north central area of the Democratic Republic of Congo, where the mystery ape lives, is known to be populated by chimpanzees. The nearest gorillas and bonobos are hundreds of miles away.

Williams, who speaks the local language, Lingala, interviewed villagers about their sightings of the creature in the Bili forest of what was once the Belgian Congo and later the Republic of Zaire.

"Some people call them 'lion eaters' because they are so big," Williams said.

Using clever tricks
On her last trip to the region earlier this year she got within about 15 feet of the animals. With some local trackers she was able to follow the apes for several hours. Williams and the trackers used some clever tricks to lure the mystery apes.

Pictures of the 'mystery ape' are rare because the animals are skittish and aggressive. Here a researcher captured an image from afar of one of the animals with her offspring.
"One of my trackers made the sound of a duiker, a small antelope, as if it were in pain," said Williams. Four or five of the mystery primates fell for the ruse and came running to kill it.

Chimpanzees and bonobos both are carnivorous. Chimps are known to eat monkeys, and at times other chimps; bonobos catch and eat fish.

Williams also has a fascinating anecdote from a longtime resident of the region, an 84-year-old Norwegian Baptist missionary known as "Madame Liev."

"Years ago, she was driving an old truck and one of these apes walked by in front of her. It was walking bipedally (upright) and was taller than her, and she's six feet tall," Williams said.

Comparing DNA
Conservation geneticist Ed Louis at the Omaha Zoo is working on an important piece of the ape mystery also.

"We compared fecal samples from this unknown animal to the DNA of captive gorillas, bonobos, and chimps," Louis said. "Our preliminary data shows that the mitochondrial DNA is chimp-like."

But mitochondrial DNA is passed down only from the mother's side. So if this species or sub-species is a hybrid of a chimp mother and a gorilla father, current DNA would only identify information from the mother.

Tests yet to come are nuclear DNA tests: This roadmap would come from both parents.

Is it a hybrid?
If the mystery animal does turn out to be a hybrid of a chimp and a gorilla , for example, such inter-breeding would not be unique in nature. There are several examples of different species breeding successfully, said Louis.

There are hybridized green sea turtles and hawksbill turtles, as well as some hybrids of Borneo and Sumatran orangutans.

Such pairings "can throw a monkey wrench in our idea of species," Louis said.

Louis said he's eager to examine further samples from the mystery ape.

Williams hopes to return to the African habitat this autumn.

She's already working on some tactics to improve her observation. She'll camouflage her skin because the animals have not seen light-skinned humans. She'll also follow the animals and try to camp out near them overnight, and she'll set up three more observation platforms near the animals' nests.

Wednesday, October 1st, 2003, 02:42 PM
URL please, Polak?

Wednesday, October 1st, 2003, 04:34 PM
Here it is:


URL please, Polak?

Dr. Solar Wolff
Thursday, October 2nd, 2003, 06:33 AM
The whole new ape thing has implications regarding classification of the human line. Genetic distance or the old morphospecies concept imply reproductive isolation--they imply a species which is, of course, reproductively isolated from other species. In Homo we have a situation in which old and new "species" overlap in time. An example of this is the sapiens / neanderthal in Europe, also the sapiens/ H. erectus overlap in Asia. If they are able to "interbreed", this yeilds either old or geographically distant and old genes into the hybrid population. Of course these ancient people didn't care at all but it would lead to systemic confusion today. This is why classification using genes is preferable over using bones, but I am still suspicious of genetic distance being used to imply reproductive isolation.