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Why is there only one human species?

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Why is there only one human species?

By Michael Mosley BBC

23 June 2011 Last updated at 08:07 GMT

The first human species to walk fully upright, Homo erectus

Not so very long ago, we shared this planet with several other species of human, all of them clever, resourceful and excellent hunters, so why did only Homo sapiens survive?

Huge debates rage about human origins, but the broad consensus among scientists is that all the different species of human that have ever existed were descended from ape-like creatures that walked upright in Africa more than six million years ago.

These creatures had many descendants, most of which became extinct, but the first creature we would recognise as human first appeared in Africa two million years ago.

Known as Homo ergaster, they made tools and were proficient hunters. His bones suggest he would have been a powerful runner, capable of speeds that would rival a modern Olympic athlete.

H. ergaster seems to have evolved during a long period of terrible drought which dried out tropical rainforests and created vast deserts.

This human species was equipped to cope with heat. They would have been smooth and largely hairless, allowing them to sweat more efficiently. H. ergaster could also travel and hunt in the middle of the day, when most animals rest.

And we know that he travelled long distances because he did not stay in Africa. A hungry meat eater, ergaster became the first human to leave Africa and colonise Asia.

Here, in a new and lush environment, he evolved and got a new name, Homo erectus.

Archaeological records show they spread over an area ranging from Turkey to China, but the population may not have been that large.

_53616157_humans_304_bbc.jpg

"These were small groups of hunters and gatherers," says Professor Chris Stringer, an anthropologist at the Natural History Museum.

"These are people that are being very mobile, in open country, to get to their food ahead of the competition. So in that sense, they're very like us in terms of their overall body shape and body build."

Supervolcano

Recent findings suggest that Homo sapiens also left Africa, around 120,000 years ago.

We travelled in small numbers, possibly no more than 100 in the first wave. Then we spread out, with some eventually reaching Europe, then occupied by the Neanderthals, while others moved east until they reached India. There is archaeological evidence that they arrived just in time for a truly cataclysmic event.

About 74,000 years ago Mount Toba, a volcano in South East Asia erupted in spectacular fashion, the biggest explosion in the last two million years. Because of its magnitude it is classed as a supervolcanic eruption.

The volcano spewed enough sulphur into the atmosphere to lower world temperatures by several degrees and enough molten rock to cover an area the size of Britain to a depth of 10 metres.

It also produced vast amounts of ash. Driven by the winds, clouds of white Toba ash covered huge swathes of Asia, including much of the Indian subcontinent. It can still be found today.

Whether it was the effects of Toba, or the arrival of modern humans, the eruption marks the high tide of erectus' occupation of Asia.

Over the next 40,000 years they were slowly driven out, probably by a combination of climate change and the effects of being out-competed for scarce food by the spread of modern humans.

Homo erectus

_53620186_erectus_bbc_302.jpg

 

  • Large face and teeth
  • Strong, pronounced brow ridge
  • Long, low skull
  • Brain 2/3 human size
  • Powerful legs

 

Stiff competition

Yet Homo erectus was slightly bigger and more powerful than Homo sapiens, so why did we thrive when they did not? The most obvious answer is that we had bigger brains - but it turns out that what matters is not overall brain size but the areas where the brain is larger.

"The Homo erectus brain did not devote a lot of space to the part of the brain that controls language and speech," said John Shea, professor of palaeoanthropology at Stony Brook University in New York.

"One of the crucial elements of Homo sapiens' adaptations is that it combines complex planning, developed in the front of the brain, with language and the ability to spread new ideas from one individual to another.. "

Planning, communication and even trade led, among other things, to the development of better tools and weapons which spread rapidly across the population.

The fossil records suggest that H. erectus went on making the same basic hand axe for more than a million years.

Our ancestors, by contrast, created smaller, more sophisticated weapons, like a spear, which can be thrown, with obvious advantages when it comes to hunting and to fighting.

The same advantages helped Homo sapiens outcompete another rival human, the Neanderthals, who died out about 30,000 years ago as the Ice Age limited available food supplies.

"Even 100,000 years ago, we've still got several human species on Earth and that's strange for us. We're the only survivors of all of those great evolutionary experiments in how to be human," says Stringer.

H. erectus hung on in Asia until 30,000 years ago. Although they went extinct, they appear to have left descendants on the island of Flores in Indonesia.

These humans, Homo floresiensis, also known as "Hobbits", survived until around 12,000 years ago. And then they went, leaving us as the last human species on the planet.

"There's such a huge gulf between ourselves and our nearest primate relatives, gorillas, chimpanzees and bonobos," said Dr Shea.

"If that gap were populated by other hominids, we'd see that gap as not so much a gulf but rather a continuum with steps on the way. We'd still think of ourselves as special, but maybe not so special - a little dose of humility wouldn't hurt.

Source.

Edited by tripsis

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Homo floresiensis

interesting tidbit about these little fellas(is it accurate??) is that the team that found them spoke to local villagers and the oldest remember being told horror stories about the "hobbit" so perhaps 12,000 yrs ago is not quite accurate.

Alledgedly the "hobbit" was quite a little theif to the local villagers and one day they stole a child, revenge was brutal. The villagers went up to the mountain and killed all they saw and then set fire to the cave system they lived in.

Since then no-one was allowed back as it was considered taboo... did they kill them all??????

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Where did you read that Moses?

Apparently, there have been (unconfirmed) modern day sightings of them, but the CIA are covering it up for some undisclosed reason...or so I read in a book on neurology.

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The 1st homo sapien king instituted the 1st baby bonus scheme, also known colloquilly as Fornicating Under Command of the King or FUCK'ing. Ever since homo sapiens have FUCK'ed their way to victory through out breeding and inter breeding with their competition. Freaky homo's lol :unsure:

Edited by Bretloth

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Where did you read that Moses?

Apparently, there have been (unconfirmed) modern day sightings of them, but the CIA are covering it up for some undisclosed reason...or so I read in a book on neurology.

 

the first documentary i saw on tv had the archeology team talk to villagers to gain any local knowledge and they were kinda gob smacked when they were told that story, the vilage elders didnt like to speak to much about it because it was a dark day in their history(got the impression the violence was not to everyones liking) this doco was the first released after the discovery, the world was still debating what they were.

If it's being covered up you may find the docos hard to find or heavily edited.

i've not heard or seen any other mention of this in any other article since(which ive found strange) so you may be right about it being hushed up??

Would take nothing more than a couple of fly overs with thermal imaging to confirm or deny

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I've heard that story too! I can't remember where. Might've been a Lloyd Pye talk on human origins or this book by Max Egan which is full of historical oddities.

Edited by The Dude

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Thanks for that, Tripsis.

Reading this, and climbing down the ladder of the internet for further reading, has been the highlight of my day.

I hated history in high-school... memorising dates of when Hadrian built his wall and when Nero fiddled on his rooftop. So insignificant compared to thinking about this sort of stuff.

History (or pre-history) has become one of my favourite topics as an adult and it shocks me that the teaching I received as a high-school student was so inane. Did I just have bad history teachers or did everyone get taught the same crap - with all the good bits left out?

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probably a bad teacher. yeah there are curriculums, but modern history was pretty much my favourite subject at school. that's not saying much, but yeah, it was good :)

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It's fascinating thinking about how our ancestors cohabited with other humans or humanoids. Imagine if there were other human species around today! We would be able to learn so much about ourselves. I wonder if we would have been able to communicate with them?

Did I just have bad history teachers or did everyone get taught the same crap - with all the good bits left out?

Pretty sure the average curriculum only covers ancient (back to maybe 4000 B.C.) and modern history. Paleoanthropology isn't a subject that is touched much in high school I guess.

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The little dudes of tribal mythology are the Ebu Gogo:

http://en.wikipedia.org/wiki/Ebu_Gogo

I think the documentary you're talking about might be this:

http://en.wikipedia.org/wiki/The_Incredible_Human_Journey

and here's a news article about them:

http://www.telegraph.co.uk/news/worldnews/asia/indonesia/1475280/Villagers-speak-of-the-small-hairy-Ebu-Gogo.html

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Thanks for those links Undergrounder, there's some interesting reading there.

Interestingly, we did find lumps of dirt with black hair in them this year in the Hobbit levels, but don't know yet if they're human or something else. We're getting DNA testing done, which we hope will be instructive.

Any idea what happened with that testing?

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There's still a lot of controversy surrounding floresiensis. They are still not sure whether it is a unique species, a dwarf erectus/australopithecus/neanderthal or dwarf homo sapien or whether some breeding between homo sapien and an earlier proto-floresiensis took place or whether the dwarfism is a genetic disorder. Same with the 'hobbits' they found in a cave in Palau, Phillipines. In a way it has been 1 species in a way for a long time that branches off and then crosses paths again. Erectus/Ergaster branched off into neanderthals and homo sapien, then as homo sapien left africa, they meet again, some mating occurs, neanderthals are wiped out or assimilated into the homo sapien population. The lineage branches off and recombines again later. It's also possible that some erectus survivors in asia were assimilated into the populations of newer homo sapiens. Genetic flow was possible between neanderthal and homo sapien and it is also theoretically possible from erectus to homo sapien. We also dont know if Neanderthal existed in asia. We can only study their known range from fossils but that doesn't mean they weren't in asia or elsewhere.

Be cool to go back in time and hang out with a peaceful group....with a BIC lighter...

Edited by botanika

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It's fascinating thinking about how our ancestors cohabited with other humans or humanoids. Imagine if there were other human species around today! We would be able to learn so much about ourselves. I wonder if we would have been able to communicate with them?

 

Yeti?

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I don't think that the supposed other homo species where infact true species, more sub species of the genera homo. The latest dna evidence shows europeans interbred with neanderthal, melanesians interbred with the denisovian homonid etc. Just one big family that gets seperated and rejoins everynow and again. I think the biblical tale of the watchers repressents a cultural memory of this, and advanced race probably cro magnon which is repressentitive of a neanderthal and sapien cross had developed abstract art before their african counterparts, where watching the skies as evidenced by early monolithic constuctions and understood higher arts like pottery and metal working. All of which where passed onto sapien cultures in the levant supposedly by fallen angels or the watchers, their offspring producing the nephilim, who have been called giants despite the hebrew word that is translated as giants actually meaning those who had fallen, interbreeding between sub species can produce freaky mutants who could have been considered to 'have fallen' so to speak in an elitist/slave culture. I think that is where we learnt our dominator culture, as the cro magnon man was physically imposing and far more advanced than early sapiens coming out of africa through the levant, I think enslaving them, and making them worship them as the sons of god, an abstract concept passed onto us from the dominator culture of the cro magnon. Right of might took hold, religeon and kingship ruled in a cro magnon elite / sapien slave culture, (check out the big white dudes who kicked off ancient egypt, enslaving the native populace). Few thousand years interbreeding, a few cataclysms, wars and despersals and the modern rientergration once more and there you go, fruit salad sapiens.

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http://erectuswalksamongst.us/

'… there is less mtDNA difference between dogs, wolves, and coyotes than there is between the various ethnic groups of human beings..." (Coppinger, 1995). It seems that taxonomists have been bending their objectivity a bit.

Now let’s see how taxonomists have classified Neanderthals. Until the 1960s, Neanderthals were classified as Homo neanderthalensis, a different species from us, Homo sapiens. But the genetic distance between Homo sapiens and Homo neanderthalensis (<0.08%) 20 is less than the genetic distance between the two chimpanzee species (0.103). 21 Today, Neanderthals are classified as Homo sapiens neanderthalensis, 22 a sub-species of our species, while we are another sub-species, Homo sapiens sapiens. The genetic distance between (sub-Saharan) Africans and Eurasians (0.2%) is more than twice the genetic distance between living humans and Neanderthals (0.08%) 23 so, at the very least, Africans should be classified as a sub-species, Homo sapiens africanus and Eurasians as another sub-species, Homo sapiens eurasianensis.

...the genetic distance between Homo sapiens and Homo erectus is estimated as 0.170 24 (mean given as 0.19), 25 about the same as the genetic distance between the Bantu Africans and the Eskimos, but the genetic distance between living Africans and Eurasians is 0.23 (Table 7-1, p. 45). Thus, Homo sapiens is more closely related to Homo erectus than Eurasians are to sub-Saharan Africans. Either erectus should be reclassified as Homo sapiens erectus or sub-Saharan Africans should be reclassified as Homo africanus. 26'

Edited by botanika

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It doesnt bode well when a study gets the nomenclature incorrect. Neanderthals were also Homo sapiens for a start, so to compare 'Homo sapiens' to neaderthals is to compare the same - Cro-Magnon man was Homo sapiens sapiens whereas Neanderthals Homo sapiens neanderthalensis, the former more clearly associated with modern humans than the later, although europeans contain the DNA of both.

It is unusual that there is only one species here but nowdays because of frequent contact and inter-relations it is unlikely that any group of humans will officially break off - the two reasons this occurs is usually isolation or competitive advantage.

The chinese often claim that the Han people descended directly from Homo erectus in asia separately from the rest of Homo sapiens sapiens. This ofcourse is bullshit.

I dont know about those little guys from Indonesia. There was some dodgy science involved there at the end, but from gnomes or Firbolgs, there have always been OTHERS around us.

Edited by Zen Peddler BlueGreenie

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There is still debate whether Neanderthals were a subspecies of Homo sapiens, or whether they were a distinct species. You say they're a subspecies, the author or the article obviously considers them a separate species. Who's to say your are right?

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It doesnt bode well when a study gets the nomenclature incorrect

The article states they were classified until the 60's as 'homo neanderthalensis' and are now currently classified 'Homo sapiens neanderthalensis'. Accordinging to Wikipedia: 'Neanderthals are classified either as a subspecies (or race) of modern humans (Homo sapiens neanderthalensis) or as a separate human species (Homo neanderthalensis).[1]' How is the author getting the nomenclature incorrect, when taxonomy is ambigous (as Tripsis kind of pointed out), either/or (as Wiki states) and inconsistent (as the author points out himself)?  Where does taxonomy draw the line between what is a species and what is not? There are recognised separate species or sub-species of Gorilla, Chimpanzee and Orangutan yet humans often with greater genetic distances between races are labelled 'all one race'. If floreseinsis was found to still be alive today would it be a separate species or would it be classed as part of the PC modern human race that is 'all equal except for trivial physical characteristics'? Likewise if sub Saharan Africans died out 40,000 years ago would archaeologists recognize them as a separate species or include them as the PC modern human race - homo sapien sapien? Hypothetical questions - not directed at anyone.

The chinese often claim that the Han people descended directly from Homo erectus in asia separately from the rest of Homo sapiens sapiens. This ofcourse is bullshit.

 

But they likely did have gene flow from archaic humans already present in east asia which may have included erectus as well as asiatic Neanderthal types. All it takes are a couple of successful alleles to spread through a group. There are similarities between archaic east asian remains and modern east asians that are not found in Africans. The OOA theory often uses examples of people in Africa (almost ALWAYS in north east Africa) that have caucasian or mongoloid features as 'proof' every 'modern human' evolved out of Africa, when it can be argued the other way: that 'modern humans' arose out of eurasia, ultimately from earlier Heidlebergensis types and moved south into Africa at various stages leaving their alleles in the populations present there. The mongoloid features are cold climate adaptations, not north african hot climate adaptions. Obviously we are all out of Africa from the chimpanzee's, but where did 'modern humans' truly arise and what classifies a 'modern human'. 

There are a lot of holes in the OOA and multi-regional theories which is why the 'out of eurasia' theory is worth considering because it ties in a bit of both.

Edited by botanika

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I haven't had a chance to read the full article, but with a three hour plane trip later this week I reckon it could be perfect timing.

Had a skim through a few of the sections.... seems very well written and coming from a logical and well researched angle. My initial thought when I started reading was that the author was going to be a crackpot, but delving a little deeper has made me curious.

Human evolution is one of my favourite topics to ponder... so many theories... really, who knows? Shall comment further once I've read the whole thing.

Cheers for the link, Botanika.

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Yeah man it's worth a read. I learnt a lot and most of it is passionate and leveled headed, plus it lacks corperupt sponsorship. Given the nature of the subject, there is speculation but that is adequately stated. It was written 2008 - it could be updated in light of Neanderthal genome and denisovan theories.

Edited by botanika

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My reasoning for my statement is accepted thought on the topic and more importantly the fact that they could interbreed as evidenced by European humans having traces of neanderthal genetics. When subspecies drift apart to the point where they can no longer interbreed they are no longer regional phenotype groups of the same species, they are now separate species. But as Homo sapiens sapiens were able to interbreed with the neanderthals, the conclusion is they are the same species.

Also the hypothesis that humans (Cro-Magnon / homo sapiens sapiens) evolved outside Africa has also been disproved. the DNA evidence is overwhelming.

Edited by Zen Peddler BlueGreenie

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The other theory is of course that our genetics has always been controlled and manipulated by Zeta Reticulans...

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Post up the overwhelming evidence - I'm keen to have a look.

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