# Humans and Chimps Interbreding - What does this mean?
**URL:** https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298
**Category:** Great Debates
**Created:** [May 18, 2006, 6:52pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298 "2006-05-18T18:52:14Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Jebus\_H.Christ](https://boards.straightdope.com/u/Jebus_H.Christ)
#### Post date: [May 18, 2006, 6:52pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/1 "2006-05-18T18:52:14Z")
> [@](#):
>
> IT GOES to the heart of who we are and where we came from. Our human ancestors were still interbreeding with their chimp cousins long after first splitting from the chimpanzee lineage, a genetic study suggests. Early humans and chimps may even have hybridised completely before diverging a second time.
>
> The answer might lie in a second striking observation. Reich’s team found that the X chromosome diverged later than any of the other chromosomes. One way this can arise is if natural selection has been acting unusually strongly on genes on the X chromosome. That is significant because in every animal species studied, genes that make hybrids less fertile than their parental species tend to be found on the X chromosome or its equivalent, so hybridisation can create strong selection pressures on this chromosome.
>
> The best explanation for these surprising findings - the relatively young and variable divergence dates between the human and chimp lineages, and the evidence for strong selection on the X chromosome - would be if the two lineages split sometime before the time of the first proto-human fossils, but later rehybridised (see Diagram) in a “reverse speciation” event (see “When evolution runs backwards”). Natural selection would favour those hybrid individuals whose X chromosomes carried fewest of the genes that lower fertility.
So if this hypothesis is proven to be true what would it mean for how we think about mankind?
Is this likely to be proven?
> **[Did humans and chimps once interbreed?](https://www.newscientist.com/article/mg19025525-000-did-humans-and-chimps-once-interbreed/?ignored=irrelevant)**
>
> Our human ancestors were still interbreeding with their chimp cousins long after first splitting from the chimp lineage, a genetic study suggests
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### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [May 18, 2006, 7:00pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/2 "2006-05-18T19:00:36Z")
> [@Jebus H. Christ](#):
>
> So if this hypothesis is proven to be true what would it mean for how we think about mankind?
>
> Is this likely to be proven?
>
> [http://www.newscientist.com/article/mg19025525.000-did-humans-and-chimps-once-interbreed.html](http://www.newscientist.com/article/mg19025525.000-did-humans-and-chimps-once-interbreed.html)
It’s not really all that earth-shattering since we already know we derive from the same species. This is just about the details. Nature doesn’t respect our concept of “species”, and there is cross-breeding between what we call species all the time.
The 4M year gap is a bit surprising, and maybe that won’t hold up over time, but we know that chimps and bonobos can interbreed and they diverged from each other about 2M years ago. They don’t interbreed in the wild because their populations are separated by a very wide river.
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### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [May 18, 2006, 7:10pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/3 "2006-05-18T19:10:45Z")
Let me add that your thread title gets it wrong. The interbreeding is between human and chimp ancestors. The human ancestor doing the interbreeding would not be a member of the genus _Homo_, and hence would not be considered “human”. If that species were alive today, you’d see it in a zoo, not living next door.
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### Author:  [@Spectre\_of\_Pithecanthropus](https://boards.straightdope.com/u/Spectre_of_Pithecanthropus)
#### Post date: [May 18, 2006, 7:15pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/4 "2006-05-18T19:15:07Z")
> [@John Mace](#):
>
> Let me add that your thread title gets it wrong. The interbreeding is between human and chimp ancestors. The human ancestor doing the interbreeding would not be a member of the genus _Homo_, and hence would not be considered “human”. If that species were alive today, you’d see it in a zoo, not living next door.
Well, obviously you haven’t seen my neighbors!
Courtesy of the “Low Hanging Fruit and Fish In A Barrel” department.
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### Author:  [@LonesomePolecat](https://boards.straightdope.com/u/LonesomePolecat)
#### Post date: [May 18, 2006, 7:16pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/5 "2006-05-18T19:16:15Z")
> [@John Mace](#):
>
> Let me add that your thread title gets it wrong. The interbreeding is between human and chimp ancestors. The human ancestor doing the interbreeding would not be a member of the genus _Homo_, and hence would not be considered “human”. If that species were alive today, you’d see it in a zoo, not living next door.
Actually, I think this is a pretty good explanation for soccer hooligans …
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### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [May 18, 2006, 7:26pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/6 "2006-05-18T19:26:53Z")
One implication of this theory (not mentioned in the linked article) is that it casts doubt on certain fossils like _Sahelanthropus tchadensis_, whose disoverors claim it to be a 7M year old upright human ancestor. It’s hard to imagine a knuckle-walking ape and an upright walking ape viewing each other as mating partners. Frankly, I thought the claims for that species being upright were a bit shaky, to say the least. In fact, there is some contention that it represents a gorilla ancestor and not a human ancestor.
(BTW, the OP did get his title from the linked article, so he really can’t be blamed for the error I noted above.)
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### Author:  [@Jebus\_H.Christ](https://boards.straightdope.com/u/Jebus_H.Christ)
#### Post date: [May 18, 2006, 7:31pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/7 "2006-05-18T19:31:35Z")
One question this brought up for me was I thought that the human line split from the ape line before the chimp and gorilla lines split. So would humans be breding with a common anestor to both the chimp and gorilla? Or am I getting things totally wrong?
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### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [May 18, 2006, 7:38pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/8 "2006-05-18T19:38:07Z")
> [@Jebus H. Christ](#):
>
> One question this brought up for me was I thought that the human line split from the ape line before the chimp and gorilla lines split. So would humans be breding with a common anestor to both the chimp and gorilla? Or am I getting things totally wrong?
That’s a good point, and I was thinking along the same lines, too. But I think what they’re saying is that line split 10M years ago, then merged again briefly about 5.5M years ago. The gorilla is thought to have split off 7M years ago, so that would be before the interbreeding took place.
Of course, this assumes that there was no interbreeding in that 4M year gap, which seems very suspicious. Also, someone needs to do this analysis between human and gorilla and chimp and gorilla to get the whole story. Man, there might’ve been some wild sex going on back then!!! 🙂
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### Author:  [@NurseCarmen](https://boards.straightdope.com/u/NurseCarmen)
#### Post date: [May 18, 2006, 7:58pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/9 "2006-05-18T19:58:04Z")
Sure I was horney, but I was really only dating her for her brains[sup]\*[/sup].
[sup]\*[/sup]they were delicious.
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### Author:  [@ElvisL1ves](https://boards.straightdope.com/u/ElvisL1ves)
#### Post date: [May 18, 2006, 8:02pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/10 "2006-05-18T20:02:17Z")
> [@John Mace](#):
>
> It’s hard to imagine a knuckle-walking ape and an upright walking ape viewing each other as mating partners.
There are a few couples I remember from high school, let’s just say …
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### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [May 18, 2006, 8:05pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/11 "2006-05-18T20:05:49Z")
> [@ElvisL1ves](#):
>
> There are a few couples I remember from high school, let’s just say …
Well, we’re pretty sure that Laura is human!
might as well get that one out of the way. 🙂
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### Author:  [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)
#### Post date: [May 18, 2006, 8:52pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/12 "2006-05-18T20:52:40Z")
> [@John Mace](#):
>
> The human ancestor doing the interbreeding would not be a member of the genus _Homo_, and hence would not be considered “human”. If that species were alive today, you’d see it in a zoo, not living next door.
You must live in a more upscale neighborhood than mine. 😕
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### Author:  [@Captain\_Amazing](https://boards.straightdope.com/u/Captain_Amazing)
#### Post date: [May 18, 2006, 9:04pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/13 "2006-05-18T21:04:20Z")
> [@Jebus H. Christ](#):
>
> One question this brought up for me was I thought that the human line split from the ape line before the chimp and gorilla lines split. So would humans be breding with a common anestor to both the chimp and gorilla? Or am I getting things totally wrong?
You’re getting things wrong. We’ve known for a while that chimps and humans are more closely related to each other than either of us are to gorillas.
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### Author:  [@Voyager](https://boards.straightdope.com/u/Voyager)
#### Post date: [May 18, 2006, 9:10pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/14 "2006-05-18T21:10:22Z")
> [@John Mace](#):
>
> One implication of this theory (not mentioned in the linked article) is that it casts doubt on certain fossils like _Sahelanthropus tchadensis_, whose disoverors claim it to be a 7M year old upright human ancestor. It’s hard to imagine a knuckle-walking ape and an upright walking ape viewing each other as mating partners.
Well, considering how some people feel about sheep 😃
The bit I read in the Times this morning seemed to indicate that _Sahelanthropus tchadensis_ represented the pre-divergence state, and evidence for convergence came from DNA. If _Sahelanthropus tchadensis_ were not a direct ancestor, I don’t think I’d get why the time of the only divergence couldn’t be taken from the DNA evidence. Given a convergence, doesn’t the DNA indicate the time of the last interbreeding? It could have been going on at any point before that.
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### Author:  [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)
#### Post date: [May 18, 2006, 9:10pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/15 "2006-05-18T21:10:33Z")
> [@John Mace](#):
>
> Man, there might’ve been some wild sex going on back then!!! 🙂
Wild monkey sex, even.
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### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [May 18, 2006, 9:11pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/16 "2006-05-18T21:11:05Z")
> [@Captain Amazing](#):
>
> You’re getting things wrong. We’ve known for a while that chimps and humans are more closely related to each other than either of us are to gorillas.
Wow, I completely misread his post the first time. You’re right-- the conventional wisdom is that gorillas split off 1M years before the human and chimp/bonobo lines split.
But like I said earlie, this new data means we need to go back and look at the gorilla and chimp and the gorilla and human DNA comparison using the same technique. We may find intermingling of the ancestors of all 4 lving African apes (putting humans in the category of “African ape” for easy of labeling).
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### Author:  [@Jebus\_H.Christ](https://boards.straightdope.com/u/Jebus_H.Christ)
#### Post date: [May 18, 2006, 9:48pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/17 "2006-05-18T21:48:53Z")
I was discussing this on another board and a poster said:
> [@](#):
>
> The ToE states that the member of a new species is, by definition, unable to create viable offspring by mating with the preceding species.
>
> If one species COULD interbreed with a previous species, then they are NOT DIFFERENT SPECIES. They are, at best, different genera or varieties of the same species, within a single family; much the same as dogs, wolves and foxes are all members of the same family.
>
> […] “Humans & Chimps Interbred” is an oxymoron
And I am not sure how to respond. I think part of the problem is his defintion of species is wrong and too rigid. But I haven’t studied biology since college. How would you respond?
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### Author:  [@Sunrazor](https://boards.straightdope.com/u/Sunrazor)
#### Post date: [May 18, 2006, 10:07pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/18 "2006-05-18T22:07:10Z")
> [@ultrafilter](#):
>
> Wild monkey sex, even.
Is there any other kind of monkey sex to have?
Would it be completely inappropriate to make a smirking comment about King Kong and Ann Darrow here? Uhm, yeah, now that I see it in print … it would be.
If my next door neighbors are silver-backed apes, are they “Gorillas In Our Midst”? (I gotta’ get myself a drummer for the rim shots!)
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### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [May 18, 2006, 10:10pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/19 "2006-05-18T22:10:51Z")
> [@Jebus H. Christ](#):
>
> I was discussing this on another board and a poster said:
>
> And I am not sure how to respond. I think part of the problem is his defintion of species is wrong and too rigid. But I haven’t studied biology since college. How would you respond?
Two populations are considered different species if they cannot interbreed or if they don’t interbreed in the wild to a signficant extent. But cross fertility between species is extremely common, in the lab if not in the wild. For instance, all sepcies in the genus [\*Canis \*](http://en.wikipedia.org/wiki/Canis) can interbreed. Wolves and coyotes even interbreed in the wild, but not often enough to be considered the same species.
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### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [May 18, 2006, 10:23pm UTC](https://boards.straightdope.com/t/humans-and-chimps-interbreding-what-does-this-mean/357298/20 "2006-05-18T22:23:11Z")
> [@](#):
>
> If one species COULD interbreed with a previous species, then they are NOT DIFFERENT SPECIES. They are, at best, different genera or varieties of the same species, within a single family; much the same as dogs, wolves and foxes are all members of the same family.
Let me pick this apart even further because this person does not know what he or she is talking about.
Different “genera” would be at a higher level of classification than the species level. He means “race” or “subspecies”, not “genera”. Further, he uses the term “family” incorrectly, as that is a level above “genus”. The hierarchy is:
Family
Genus
Species
As I said above, [the list of species that can interbreed is quite long](http://en.wikipedia.org/wiki/Hybrid). Many can even produce fertile offspring. There are even species in different genera that can interbreed. But as long as they don’t form a a continuous interbreeding population in the wild, they are considered different species.
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