Why only "out of Africa?"

[Itoero]

On ‎16‎/‎08‎/‎2018 at 10:11 PM, mistermack said:

Complex social groups do encourage some intelligence, but there are plenty of monkeys and apes who live in similar groups. 

We have complex language….In social groups, you communicate for better group cohesion. Our communication system is far better developed then the one of other animals.

[mistermack]

59 minutes ago, Itoero said:

We have complex language….In social groups, you communicate for better group cohesion. Our communication system is far better developed then the one of other animals.

Yes, we are certainly unique in loads of ways. 

But going on the fossil record, eight million years ago, our ancestors, and those of Gorillas, Chimps and Bonobos were the same ape. Over those eight million years, Gorillas split off, and then Chimps and Bonobos, from us. (or we split from them, same thing)

They are all social apes, just like us, but we evolved the big brains and the language skills, and they didn't. So it wasn't living in big social groups that made the difference between us and them. It might be that improving language skills kick started intelligence gains. Or vice versa. But it would be hard to prove now. 

[jaym04]

I think environment has a great influence on how they evolved.

 

[mistermack]

On 8/20/2018 at 5:39 AM, jaym04 said:

I think environment has a great influence on how they evolved.

Of course that's right. But in fact, for most higher animals, the most important part of their environment is their own kind. 

It's certainly true for us, and for our closest relatives. And the latest evidence is that our ancestors began to separate from those of Chimpanzees and Gorillas in a similar forested environment. 

[CharonY]

On 8/23/2018 at 6:39 AM, mistermack said:

But in fact, for most higher animals, the most important part of their environment is their own kind. 

Do you mean that social interactions are more relevant than environmental in higher animals? Does "higher" mean complex here? If so, how about solitary species? If not, could you elaborate on that?

[mistermack]

1 hour ago, CharonY said:

Do you mean that social interactions are more relevant than environmental in higher animals? Does "higher" mean complex here? If so, how about solitary species? If not, could you elaborate on that?

Well, you can probably quote exceptions, but in general, your own species is the most important part of your life. Especially for mammals, which are cared for from birth by a mother. Even mammals that are often thought of as solitary, have a lot of interaction with others beneath the surface. Male Tigers might be thought of as solitary, but they needed their mother for a couple of years, and learn to fight and hunt in play with their siblings. Also, when adult, they try to maintain a territory overlapping with several females, and often get killed defending it. 

Lots of mammals are territorial, such as Humans, Lions, Tigers, Gorillas, Wolves, Hyenas etc. And of course, what is a territory, but some area that you defend from others of your own kind.

Going through random animals in my head, very few could be considered truly solitary. Snakes maybe, once reproduction is over. But not all snakes. Maybe some birds. But other birds are territorial, and sing and fight to keep what they have. Others live in flocks, and reproduce in colonies. Others mate for life with the one partner. Which is the most important part of life.

Edited August 27, 2018 by mistermack

[CharonY]

I am not sure whether such a broad definition is useful. From that standpoint even for unicellular organism the parental cells and its status are defining their survival or existence, for example. Bacteria have evolved mechanisms to kill members of their own species so it is not even limited to higher organisms. At minimum it would put all sexually reproducing organisms and again, not sure how that is useful

And on the opposite end you could argue that it still account for nothing if e.g. the environment does not provide access to nutrition. I.e. while there are inter as well as intraspecies competition, all still happens on the backdrop of the ecological system they are living in. Trying to isolate one over the the other does not seem, well, useful.

 

[mistermack]

It could be useful, in the sense that if you want to explain some feature of an animal, it pays not just look at the environment, without including others of the same species. 

If you take humans as an example, and look at our ancestors 7 million years ago, the fossils show very long canines in males, and a male body size of twice that of females. That all makes sense, if our ancestors lived in family groups like those of gorillas, where one dominant male monopolises a harem of females. So you can tell something about how they interacted by looking at the bones. Sexual dimorphism on that scale is always an indicator of a harem type grouping, as in Gorillas, Lions, Baboons, Sea Lions etc. 

Our canines shrank, and male/female size ratio also shrank, and that indicated a shift in the male/female relationship, from harems to bonded pairings. 

On the subject of this thread, I think it's most likely that we evolved the big brain to successfully negotiate relationships and alliances in a dangerous and violent system of communal living. Rather than in response to any more conventional environmental stimulus. 

 

[CharonY]

3 minutes ago, mistermack said:

It could be useful, in the sense that if you want to explain some feature of an animal, it pays not just look at the environment, without including others of the same species. 

If you take humans as an example, and look at our ancestors 7 million years ago, the fossils show very long canines in males, and a male body size of twice that of females. That all makes sense, if our ancestors lived in family groups like those of gorillas, where one dominant male monopolises a harem of females. So you can tell something about how they interacted by looking at the bones. Sexual dimorphism on that scale is always an indicator of a harem type grouping, as in Gorillas, Lions, Baboons, Sea Lions etc. 

Our canines shrank, and male/female size ratio also shrank, and that indicated a shift in the male/female relationship, from harems to bonded pairings. 

On the subject of this thread, I think it's most likely that we evolved the big brain to successfully negotiate relationships and alliances in a dangerous and violent system of communal living. Rather than in response to any more conventional environmental stimulus. 

 

I think you are missing my point. In any thorough study, the intra-species interactions are part of the parcel. Depending on features you are looking at they can be a driving factor. However, they are embedded in their given environment and you can generally not understand these adaptations without that context. 

The issue is specifically that in your post before it seems you noted the following as fact:

Quote

But in fact, for most higher animals, the most important part of their environment is their own kind. 

With the issue of not defining a) what higher animals are and demonstrating that b) these interactions are indeed the most important kind (with which I assume selective pressures are meant). An overall issue is of course the lack of precision here. Intra-species interactions, including mate selection are of course a major driver for certain aspects (including social interactions, mating behaviour etc.). But making it a general statement makes it inaccurate. Trying to expand the scope by including all interactions kind of diminishes the overall point and, as I noted, would include the most simplest of organisms.

[mistermack]

I think it's nit picking a bit. What I said was accurate. We all need others of our species to pass on our genes. I was simply pointing out that the external environment is necessarily number two in importance, something that a lot of people don't seem to get. It's the stress on the external environment for influences that I was pointing at. It's  not the be-all and end-all of evolution. 

And it's not just your own species. Very often, things evolve in response to other species. Like the pronghorn antelope was a bit of a mystery, till they discovered the fossils of the American Cheetah, explaining what was forcing the pronghorn to evolve such speed. I'm just saying that the word environment really includes everything, and your own species is usually at the fore.

[CharonY]

28 minutes ago, mistermack said:

I think it's nit picking a bit. What I said was accurate. We all need others of our species to pass on our genes. I was simply pointing out that the external environment is necessarily number two in importance, something that a lot of people don't seem to get. It's the stress on the external environment for influences that I was pointing at. It's  not the be-all and end-all of evolution. 

And it's not just your own species. Very often, things evolve in response to other species. Like the pronghorn antelope was a bit of a mystery, till they discovered the fossils of the American Cheetah, explaining what was forcing the pronghorn to evolve such speed. I'm just saying that the word environment really includes everything, and your own species is usually at the fore.

All of science is nitpicking and grand statements have to supported with equivalent levels of evidence. Anything else is making up stories. Sexual dimorphisms are often related to mate selection (not necessarily polygyny, just intense male-male competition). That is what I offered above. However, you cannot, for example reduce all or even much of the development to such simple explanation.

Take Australopithecus. Here, we have the case of large sexual body dimorphism in size, yet reduced canine dimorphism. The latter of which indicating reduced male-male competition but conflicts with the former. In contrast to what you present, those aspects are still very much under discussion and there is almost no trivial answer to those complex questions. Also note that even if you want to discuss dental evolution, there is the added issue of diet is known to shape the need to maintain canines. 

Intra-species pressures are really just one bit of the puzzle. You are taking one aspect that are specifically driven by mating behaviour and ignore all the other aspects of influences and thus proclaim that that is the main driving force. It is rather funny as sexual selection was identified specifically to understand certain developments that did not make sense otherwise (like peacock feathers), only here it is kind of flipped around.

Point is, intraspecific competition has its place to explain certain aspects (e.g. sexual dimorphisms) but will utterly fail in explaining most other evolutionary traits (activity cycle, non sex-dependent body size, metabolism, sensory adptations etc etc). 

Edited August 27, 2018 by CharonY

[mistermack]

Well, I think you've forgotten where these posts are. This is a thread on a forum, not a textbook. And the subject is "why only out of Africa?" and I'm simply pointing out that Africa itself is probably not the significant factor, but our interaction with our peers probably was. I'm simply sticking to the point of the thread. 

In the case of Australopithecus, it could be that the canines became redundant, once males began using weapons, but body size was still an advantage. Or even that females preferred males with smaller canines, and that took effect once the fighting advantage of big canines was nullified by using weapons. Once we became bipedal, the nature of fights would be likely to change, and it's unlikely that Australopithecus could have survived without skills with weapons. A newly bipedal ape would have been very slow off the mark, and a lesser climber. They would need males with weapons to survive life out of the trees.

Edited August 27, 2018 by mistermack

[Itoero]

On ‎28‎/‎08‎/‎2018 at 1:14 AM, mistermack said:

In the case of Australopithecus, it could be that the canines became redundant, once males began using weapons, but body size was still an advantage. Or even that females preferred males with smaller canines, and that took effect once the fighting advantage of big canines was nullified by using weapon

Australopithecus species ate mainly  fruit, vegetables, small lizards, and tubers. They did not have much use of their canines.

[mistermack]

34 minutes ago, Itoero said:

Australopithecus species ate mainly  fruit, vegetables, small lizards, and tubers. They did not have much use of their canines.

The big canines on most apes and monkeys are for male-male intimidation and fighting, not eating. This is obvious in Gorillas, Chimps and Baboons etc, as well as the pre-human fossils, because males have much bigger canines than females. It really isn't much of a surprise, that at the time that tool use, and presumably weapons too, was increasing, the canines started shrinking.

[CharonY]

On 8/27/2018 at 5:14 PM, mistermack said:

Well, I think you've forgotten where these posts are. This is a thread on a forum, not a textbook. And the subject is "why only out of Africa?" and I'm simply pointing out that Africa itself is probably not the significant factor, but our interaction with our peers probably was. I'm simply sticking to the point of the thread. 

In the case of Australopithecus, it could be that the canines became redundant, once males began using weapons, but body size was still an advantage. Or even that females preferred males with smaller canines, and that took effect once the fighting advantage of big canines was nullified by using weapons. Once we became bipedal, the nature of fights would be likely to change, and it's unlikely that Australopithecus could have survived without skills with weapons. A newly bipedal ape would have been very slow off the mark, and a lesser climber. They would need males with weapons to survive life out of the trees.

This is still a science forum and we try to minimize bad science on this site. And we specifically have a speculations sector for these types of guesses. My larger point is that in science there is literature to read up only because one does not have done so does not mean that one can or should state those speculations as facts. My specific point is that there actually are papers that have looked at various aspects relating to human evolution. 

Perhaps I was too subtle but I would like to invite you to look at following key words: metabolic cost of brain development, ecological and social drives of human evolution, cooperative and competitive challenges. Take a look at the literature you'll find and then try to embed and relate your assumptions to these observations.

Edited August 29, 2018 by CharonY

[mistermack]

You're not averse to a bit of speculation. You made the claim that diet is known to shape the need to maintain the canines. That's a silly claim, considering that males and females would be eating the same stuff, but males had big canines, and females didn't. Unless you are claiming otherwise, and I'd like to see your evidence for that.

[CharonY]

14 minutes ago, mistermack said:

You're not averse to a bit of speculation. You made the claim that diet is known to shape the need to maintain the canines. That's a silly claim, considering that males and females would be eating the same stuff, but males had big canines, and females didn't. Unless you are claiming otherwise, and I'd like to see your evidence for that.

You are not reading it correctly. I was not talking about sexual dimorphism in canines, but in overall canine maintenance. Specifically that canine evolution cannot be discussed exclusively in the context of mate selection. The overall function of dentition is related to the diet of the organism and while they may change to display functions, it would not easily explain significant sex-independent changes. Even if an extant species uses canine exclusively for display, for example, it must mean that there have been dietary developments allowing them not to require them for their dietary needs, for example.

Again: sexual dimorphisms are often indicators of mate competition, non-sexual developments, not so much. That, of course is the why it is an extremely limited view to argue mate selection as a major driver of speciation. Even if we take a species in which current use is mostly for display, we will have to look at its past to see where it changed in function. A thing to add is that of course there is speculation involved when it comes to evolution or, in fact most areas of sciences. The difference, however, is whether one merely extrapolates one rough idea or actually takes a look at existing knowledge.

A few reads, though I suspect a broader textbook in evolution would also be helpful:

Discussion of dietary changes in the Miocene in hominoids: Andrews and Martin, 1991, Phil Transactions Royal Soc B

Dietary use of canines in Afropithecus: Deane,  2012, J Human Evo

This one goes beyond mate selection/competition for sexual dimorphisms and looks at ecological causes (to expand the view a bit): Shine, 1989, Quart Rev Biol 

A paper on how canine reduction in early hominins is related to increased mechanical efficiency of jaws: Hylander, 2017 Human Paleo Prehis

Another one discussing the complexity between feeding, social behavior and morphology: Ross and Iriarte-Diaz, 2014, Evol Anthro

[mistermack]

You're using a lot of words to state the obvious. You'd have to be an idiot to imagine that canines were not used for eating. The fact remains that it's incredibly obvious that if females have regular canines, and males have extremely enlarged canines, then the difference is nothing to do with food. 

And the papers that you linked are of course based on the authors' speculation, which you so vehemently disapprove of. Speculation and argument put in a paper, with supporting material, is still speculation. You need to be a bit more consistent.

My own speculation matches the facts rather well. Upright apes freed their hands which allowed them to wield a weapon, to greater effect than a Chimp could. Chimps have been recorded using weapons, but they don't have the two-footed agility that a bipedal ape would. The earliest stone choppers have been found, when viewed under strong microscopes, to have fragments of fossil wood embedded in the edge. Pretty good evidence of woodworking, and cutting and sharpening wooden weapons is among the likeliest explanations. 

Of course that's speculation. So is every other proposal. And I note that you haven't linked anything better. The one about mechanical efficiency of jaws is laughable. Has nobody told the Gorillas ?    

 

[CharonY]

In other words you prefer to ignore research, ignoring (or failing to understand) that there are more factors than sexual dimorphisms shaping morphology in order to promote a particular thought?

Well, sounds like we are in soap boxing territory now. 

[mistermack]

I note that you haven't made one specific argument against the notion you've taken exception to. Just linking other speculation doesn't cut it. This is a forum for discussion, and your best argument is to post a few speculative links to other peoples' hypotheses. Which you incorrectly labelled "existing knowledge".

Why haven't you demolished what I wrote, with your own rebuttal in your own words? I would appreciate that rather more than your failed attempt to talk down to me. 

[CharonY]

I have highlighted scientific studies indicating the vast intersection environmental factors (such as diet) not only affecting dental morphology, but also sexual dimorphism related to that. You chose to ignore them. If you had specific claims supported by data there would be a way to discuss and dissect them. However, you only provide rough handwavy arguments without any scientific sources supporting your claim. Note that you elevate your own arguments to the same level as that of folks actually studying the subject and that tells me that we are now moving further away from the science territory. How about you read those papers and try to demolish them. How about specifically invalidate the impact of environmental factors on human evolution? Show me data that explains evolution of higher organism exclusively from the lens of intraspecific competition. Or at least provide data that it has, as a whole a larger impact. 

How about citing a few studies that claim it and critically discuss their findings? You, know science does not work by running with your gut feeling and unless you add science to the discussion I feel I have already wasted too much time. 

Edited August 29, 2018 by CharonY

[mistermack]

Nothing specific to answer with then. 

I thought as much. Basically, you're just blustering and googling. I'm not wasting my time any further.