# Why haven\`t todays monkeys evolved?
**URL:** https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778
**Category:** Factual Questions
**Created:** [October 6, 2003, 12:26am UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778 "2003-10-06T00:26:21Z")
**Posts on this page:** 15
**Page:** 3
### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [October 7, 2003, 8:43pm UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/41 "2003-10-07T20:43:37Z")
Colibri:
That list seems to have some strange entries:
1. Rodentia more modifed than Primates?
2. Cetacea less modified than… anything?
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### Author:  [@Revtim](https://boards.straightdope.com/u/Revtim)
#### Post date: [October 7, 2003, 8:54pm UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/42 "2003-10-07T20:54:57Z")
> [@](#):
>
> \*Originally posted by FlyingDragonFan \*
> \*\*[Here’s](http://wld.fwc.state.fl.us/critters/exotics/resultsClass.asp?taxclass=M) a page with all the exotic mammals that have established themselves in Florida. Scroll down for a breakdown. \*\*
Thanks!
And **Starrman10** , the clown line is from ‘Family Guy’, the episode where Peter and his wife run against each other for some kind of school position, and Peter’s old science teacher was the one who dissected the clown.
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### Author:  [@Algernon](https://boards.straightdope.com/u/Algernon)
#### Post date: [October 7, 2003, 9:12pm UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/43 "2003-10-07T21:12:27Z")
**Colibri** , could you say more about the logic used in creating the list you, uh, listed?
As an example, it seems to me that both Rodentia and Xenarthra are much more similar to the “low” end of your list than Primates. Admittedly I know little about these other than superficial appearance, but still…
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### Author:  [@chorpler](https://boards.straightdope.com/u/chorpler)
#### Post date: [October 7, 2003, 9:41pm UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/44 "2003-10-07T21:41:49Z")
> [@](#):
>
> \*Originally posted by The Gaspode \*
> **If you stop to think about it, it isn’t really our great big brains that make the trick. The hands is the answer. Dolphins have brains as big and complex as humans, yet the persist in living a life quite similar to chimps or any other brainy animal, i.e. Eating, copulating and raising babies.**
I thought I read somewhere that the main reason for the brain of a dolphin being so big and complex was for signal processing … since they live in a three-dimensional world and have to process a lot of sonar data and the like.
(And of course, when I say “big,” I mean in relation to body size. Obviously elephants and whales and many other big animals have brains that are larger than humans, but rather than allowing said animals to churn out Broadway musicals, they’re mostly just used as control centers for the sizable bodies they reside in.)
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### Author:  [@Mr.Obvious](https://boards.straightdope.com/u/Mr.Obvious)
#### Post date: [October 7, 2003, 9:58pm UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/45 "2003-10-07T21:58:44Z")
[/humor]
They have…one of them is the current Secretary of Defense and another is the Attorney General.
[/humor]
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### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [October 7, 2003, 10:10pm UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/46 "2003-10-07T22:10:17Z")
> [@](#):
>
> \*Originally posted by chorpler \*
> I thought I read somewhere that the main reason for the brain of a dolphin being so big and complex was for signal processing … since they live in a three-dimensional world and have to process a lot of sonar data and the like.
That’s likely to be part of the equation.
They also have very complex social lives, much like primates. Whether that is a cause or an effect of a large, complex brain is open to debate.
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### Author:  [@Colibri](https://boards.straightdope.com/u/Colibri)
#### Post date: [October 7, 2003, 11:32pm UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/47 "2003-10-07T23:32:41Z")
**John Mace** and **Algernon** :
That’s a major problem with any taxonomic sequence - the evolutionary relationships are a complex three-dimensional tree that is impossible to represent in a linear sequence.
There are several things to be considered in formulating any taxonomic sequence, including both (1) branching pattern, (2) degree of modification. In general, lineages that branched off first are placed first; but within lineages that branch at the same level the less modified are placed first.
The problem is obvious in a group like the montremes - they branched off from the rest of the mammals very early, and although they retain some very “primitive” traits they are highly modified.
Perhaps the “Walker” sequence wasn’t the best one to use, but it was handy. “Walker” is a relatively traditional sequence; the higher-level classification of mammals is in a state of flux at the moment, so it’s hard to find a good sequence.
However, [here’s](http://tolweb.org/tree?group=Eutheria&contgroup=Mammalia) a fairly recent tree (with the caveat that since it’s from 1995 it’s already a bit out of date).
Nowadays it’s generally thought that the edentates/pangolins are the most primitive eutherians (but of course, the anteaters/armadillos/sloths are all highly modified in some ways). After that, there’s little agreement on what order the other major groups branched off in.
Traditionally, Primates have been thought to be a relatively basal branch because of the evident relationship to the Insectivores (which are generally thought to be primitive) through the Tree-shrews. But this relationship is less clear than was once thought.
Relative to primates, rodents can be considered to be more “advanced” because of their extremely specialized and highly modified dentition - permanently growing incisors, loss of canines, etc.
Whales are indeed probably the most highly modified mammals. Their relative low position in the “Walker” sequence is probably due to the postulated close relationship to creodonts (now questioned), which were thought to be basal to the clade including carnivores and ungulates - so therefore whales are placed before these groups.
As I mentioned before, Primates are really relatively “generalized” mammals, with few major modifications of the skeleton compared to others. There are some adaptations for climbing, but primates generally have the primitive number of digits (five each on fore and hind limbs), have retained most of the original complement of bones present in ancestral mammals, have relatively unmodified teeth, etc. Few other groups besides the insectivores are so little modified from the basal eutherian body plan.
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### Author:  [@MelCthefirst](https://boards.straightdope.com/u/MelCthefirst)
#### Post date: [October 7, 2003, 11:32pm UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/48 "2003-10-07T23:32:50Z")
> [@](#):
>
> \*Originally posted by David Simmons \*
> \*\*Read the **John Mace** cite and then think of theories in this manner. Theories are _premises_ which are taken as correct for purposes of further study. The theory directs the way in which the studies should aim in looking for further data. If the further data is in accord with the predictions made using the theory as a guide then the theory is said to be supported by the evidence. However, it could still be incomplete, wrong in certain aspects, or just plain wrong. The latter possibility is highly unlikely for a theory like evolution which has been studied to a fare-thee-well for many years by a lot of highly able scientists.
>
> All scientists know this, accept it and are not at all bothered by seeing a theory modified. In fact, that is what virtually 100% of them want to do; _i.e._ uncover a new bit of data that will allow them to be remembered as having corrected an existing theory, or if really fortunate, propound one that is wholly new and useful.\*\*
Um, I know a few who jump up and down, pull their hair out and scream blue murder when their theories are modified. I guess its those who let ‘ego’ take over?
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### Author:  [@myles](https://boards.straightdope.com/u/myles)
#### Post date: [October 8, 2003, 12:28am UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/49 "2003-10-08T00:28:54Z")
Just to add a comment,
the common ancestor of both homo sapiens sapiens and the chimapnzee with whom we may share as much as 98% of our DNA is thought by paleoanthropologists to be “the picanthropus”. At least that was the culprit the last time I checked a couple years ago.
Now you know.
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### Author:  [@myles](https://boards.straightdope.com/u/myles)
#### Post date: [October 8, 2003, 12:33am UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/50 "2003-10-08T00:33:22Z")
That’s what I get for running off my mouth.
From Stephen Jay Gould’s Wonderful Life:
“Chimps are not ancestors but modern cousins, equally distant in evolutionary terms from the unknown forebear of African great apes and humans. Pithecanthropus (Homo Erectus in modern terms) is a potential ancestor, and the only legitimate member of the sequence.” (page 29, hardcover edition)
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### Author:  [@myles](https://boards.straightdope.com/u/myles)
#### Post date: [October 8, 2003, 12:40am UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/51 "2003-10-08T00:40:29Z")
I apologize yet again for sloppy speaking and misquoting.
I was taking a Gould quote out of context. He was not saying that Pithecanthropus was a common ancestor of chimpanzees and humans, homo erectus is much too recent for that.
However, what I should have said the very first time, If I had bothered to think before speaking, is that Ardipithecus is the closest specimen we yet have to a common ancestor.
And that is my last word, I promise.
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### Author:  [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)
#### Post date: [October 8, 2003, 1:09am UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/52 "2003-10-08T01:09:24Z")
re: relative “advancement” of rodents over primates
Consider the typical rodent dentition. The continously growing incisors are a derived feature which, in terms of divergence from the basal mammal pattern, are miles ahead of anything primates have come up with.
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### Author:  [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)
#### Post date: [October 8, 2003, 2:27am UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/53 "2003-10-08T02:27:45Z")
> [@](#):
>
> \*Originally posted by MelCthefirst \*
> \*\*Um, I know a few who jump up and down, pull their hair out and scream blue murder when their theories are modified. I guess its those who let ‘ego’ take over? \*\*
Absolutely true. I should have written that scientists don’t mind having _someone else’s_ theory modified or overturned. In the interest of brevity, I gave a wrong impression that _all_ were happy to see science advanced. I suppose ultimately all are glad to see that happen, but along the way some noses can get seriously out of joint.
In about 1830-40 or so, a Hungarian physician, Ignaz Semmelweiss, discovered and very cleverly proved, even by today’s standards, that the “disease” commonly called childbed fever was a result of contact infection from doctors’ hands. By insisting on conscientious washing in a solution of carbolic acid before and after the examination of each patient in his hospital he reduced the incidence of the disease to under 1% while in other hospitals it was as high as 40-50%.
Semmelweiss’ ideas were contrary to the conventional wisdom of the day and he was scorned and ridiculed by, among others, Robert Virchow who was a well known and able scientist. As a result Semmelweiss’ idea was ignored and not rediscovered until the time of Louis Pasteur and Joseph Lister.
The path of scientific discovery isn’t a smooth straight line from “good” to “better” but sooner or later “better” does come about.
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### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [October 8, 2003, 3:56am UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/54 "2003-10-08T03:56:51Z")
> [@](#):
>
> \*Originally posted by DrFidelius \*
> \*\*re: relative “advancement” of rodents over primates
>
> Consider the typical rodent dentition. The continously growing incisors are a derived feature which, in terms of divergence from the basal mammal pattern, are miles ahead of anything primates have come up with. \*\*
Chalk one up for the rodents. But how about:
- larger brains
- binocular vision
- opposable thumbs
- small litters (usually only one)
- extended childhoods
- reduced sense of smell
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### Author:  [@Colibri](https://boards.straightdope.com/u/Colibri)
#### Post date: [October 8, 2003, 4:13pm UTC](https://boards.straightdope.com/t/why-haven-t-todays-monkeys-evolved/205778/55 "2003-10-08T16:13:08Z")
> [@](#):
>
> \*Originally posted by John Mace \*
> \*\*Chalk one up for the rodents. But how about:
>
> - larger brains
> - binocular vision
> - opposable thumbs
> - small litters (usually only one)
> - extended childhoods
> - reduced sense of smell \*\*
These characteristics are not nearly as basic as changes to the skeleton or dentition. Primates, like any other group, have certain characteristics that define them. But they retain the fundamental body plan of primitive eutherians. The biggest skeletal changes in primates are probably the complete bony orbit around the eye. The evolution of opposable digits (found also in marsupials) is not as basic as the changes found (for example) in the ankle joint of artiodactyls. Another primate characteristic is a mobile shoulder joint (which involved the retention of the clavicle, which has been lost in many other mammals), but again, the modifications are relatively slight.
I might add that bats, despite their modifications for flight, are like primates in that many of their other skeletal and dental characteristics are relatively “primitive.” Primates similarly have a suite of characteristics connected to adaptation to a particular ecological role (arboreal living) but are otherwise primitive.
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