Rushing To Help Limbaugh Understand Evolution

A terrible tragedy unfolded this week at the Cincinnati Zoo when a rare, 17-year old silverback gorilla named Harambe was killed by zoo officials who believed it was necessary in order to save a 4-year old boy who had fallen into the animal’s enclosure. News of this story spread far and wide and reaction from the public has ranged from outrage at the zoo to outrage at the parents of the child, and everywhere in between. Many primate and zoo experts have supported the split-second decision to take the life of the gorilla, interpreting the gorilla’s behavior as threatening to the boy. Cincinnati Zoo Director Thane Maynard said he stands by the decision: “We are heartbroken about losing Harambe, but a child’s life was in danger and a quick decision had to be made by our dangerous animal response team.” Yet, there are others who claim the decision was hasty and that non-lethal methods of dispatching the gorilla could have been employed. The debate will continue as more details about the situation come to light.

But an additional issue that arose during the coverage of this story can be clarified immediately, as the answer has been known for over 150 years. Yet surprisingly in 2016, some pundits still do not understand the basic fundamental concepts of evolution.

On his daily radio show on Tuesday, May 31, 2016, conservative talk show host Rush Limbaugh had this to say about the incident at the Cincinnati Zoo. In particular, Mr. Limbaugh chose to respond to the comments of Ashley Byrne, a spokesperson for the People for the Ethical Treatment of Animals, when she was interviewed on CNN’s Newsroom, saying:

ASHLEY BYRNE: “In many circumstances gorillas have shown that they can be protective of children or small beings.  Frankly, the fact that this gorilla was innocent in the first place, that's the first place that this situation went wrong because even under the best circumstances captivity is never adequate for gorillas and other primates. And in cases like this we see that it's even deadly. And this tragedy is exactly why PETA urges families to stay away from any facility, zoos, circuses, or otherwise, that displays animals as a sideshow for humans to gawk at.”

Mr. Limbaugh, after playing this audio clip responded this way:

RUSH LIMBAUGH: “This woman obviously has not read Genesis and even if she did, it wouldn't have any impact on her. But human beings travel all over the world to gawk at animals precisely because they're unusual! They're interesting. Some are cute, some are deadly, some...There's no way human beings are gonna not be interested in animals. Gawking at them out on safari, hunting them or what have you. By the way, you know there's another factor in this, Snerdley [call screener]? A lot of people think that all of us used to be apes. Don't doubt me on this. A lot of people think that all of us used to be gorillas, and they're looking for the missing link out there. The evolution crowd. They think we were originally apes. I've always had - if we were the original apes, then how come Harambe is still an ape, and how come he didn't become one of us? [switches to dopey voice] "Well, that's why we’re looking for the missing link, Mr. Limbaugh, your question is absurd."

By switching to a mocking tone, Mr. Limbaugh seeks to insult “the evolution crowd”, yet doesn’t seem to realize the joke is on him. Mr. Limbaugh’s comments reveal a striking ignorance about the most basic premise of evolution. Evolution does not state that we came from the gorillas, apes, or monkeys that you see today. Instead, we share a common ancestor with our fellow primate species – a common ancestor that lived long ago and has long since vanished.

Below is a phylogenetic tree representing the evolutionary relationships between the living primates. Humans (hominids) and chimpanzees are most closely related and, based on an abundance of molecular genetics and fossil data, it appears that humans and chimps diverged along their own evolutionary paths at least 6 million years ago (and possibly earlier).

This is a well-established fact that deserves repeating:  humans and chimps diverged along their own evolutionary paths. So while chimpanzees and humans share a common ancestor (technically, an ancestral population because an individual does not evolve; rather, populations evolve over vast periods of time), HUMANS DID NOT EVOLVE FROM CHIMPANZEES. Furthermore, gorillas diverged from the chimpanzee/human ancestral population even further back in time, approximately 7 or 8 million years ago. This is also why gorillas did not (and will not) become “one of us”.

This is why some in the “evolution crowd” might tell you that your question is absurd - it is a clear admission that you do not understand the key principle of evolution. Perhaps the analogy conveyed in this meme will clear up your confusion about how evolution works, and how humans actually evolved.

The discovery of evolution is one of the most revolutionary insights into who we are and why we are here. We implore Mr. Limbaugh and those of his ilk to reconsider whether they wish to continue believing in a fantasy, or have the courage to embrace reality. Many religious people do not see evolution as a violation of their faith; indeed, are you not insulting your creator by refusing to apply the reason that has been gifted to you?

Contributed by:  Jason Organ and Bill Sullivan

Follow Jason on Twitter.

Follow Bill on Twitter.

For more information about human evolution check out this series of podcasts from the Leakey Foundation.

References:

Venn, O., Turner, I., Mathieson, I., de Groot, N., Bontrop, R., & McVean, G. (2014). Strong male bias drives germline mutation in chimpanzees Science, 344 (6189), 1272-1275 DOI: 10.1126/science.344.6189.1272

Glazko, G. (2003). Estimation of Divergence Times for Major Lineages of Primate Species Molecular Biology and Evolution, 20 (3), 424-434 DOI: 10.1093/molbev/msg050

A Tale Of Monkey Tails, And Why Curious George Is Not A Monkey.

“George was a good little monkey and always very curious.”

This line opens nearly every one of the adventures that Curious George has set upon since he was first brought to life by HA Rey in the 1939 children’s book “Cecily G. and the Nine Monkeys.” These stories, which have sold over 25 million copies over the last 75 years, and are beloved by child and parent the world over, begin with a lie – a big fat lie because, in fact, Curious George is NOT a monkey.

We at THE ‘SCOPE thought it would be a good idea – in this Year of the Monkey – to clarify some things about our beloved primate pal, George. So what is a monkey, and why is George not one? Generally speaking, monkeys are haplorhine primates with external tails. Another way of saying this is that they have dry, furry noses (not wet ones like lemurs or dogs or cats) with more than just the vestigial tailbone that apes have, including humans. All monkeys have tails,* although some are longer than others. And because Curious George does not have a tail (along with other reasons explained elsewhere), he is not a monkey but an ape.

Frankly, and we’re just gonna throw this out there… Curious George would be way cooler if he were a monkey, precisely because he would have a tail. And monkey tails are fascinating structures because they come in so many varieties: long, short, skinny, fat, hairy, partially bare, prehensile, nonprehensile… wait, what does that mean?

We’ll tell ya!

Prehensile tails are ones that are capable of suspending the entire body weight of the animal. So, an animal with a prehensile tail can hang from its tail, which frees up its hands and feet for other activities like picking fruit or leaves to eat. Based on observations of living and fossil species, it is generally thought that prehensile tails evolved at least 14 times independently among 40 different genera of extant mammals. And this doesn’t include all the other living vertebrates with prehensile tails, like some snakes, lizards, salamanders, and seahorses, to name a few.

Not all monkeys have prehensile tails, which is a shame for those that don’t because prehensile tails are much more interesting than nonprehensile ones. In fact, the only monkeys that have prehensile tails are in Central and South America (platyrrhines or New World monkeys), but not even all those have prehensile tails. Prehensile tails likely evolved twice in the New World monkeys that have them: once in the ateline monkeys, which include spider monkeys, woolly monkeys, howling monkeys, and muriquis, and then a second time in the capuchin monkeys.

Left: Capuchin monkey (Cebus apella); Right: Spider monkey (Ateles geoffroyi)

In most respects, both instances of prehensile tail evolution in monkeys resulted in similar anatomical structures. Monkey prehensile tails are comprised of vertebrae that are structured to resist higher bending and torsional forces. This seems intuitive because animals that hang from their tail put more stress on the bones in their tail. So having bones that can resist higher forces would safeguard against accidental fracture. The ends of these tail vertebrae are more convexly rounded at the point where they articulate with one another, which allows for a greater range of motion than in nonprehensile tails. Also fascinating is that some of the muscles in prehensile tails are structured to produce higher contraction forces than those of nonprehensile tails, while other muscles have developed shorter extrinsic tendons that cross fewer joints along the tail, enabling the animal to have tighter control of the tail to wrap around substrates.


But the parallel evolution of prehensile tails in New World monkeys has also led to some pretty interesting anatomical differences that reflect functional differences in the way the tail is used. In addition to hanging from the tail during feeding bouts, ateline monkeys use their prehensile tails during locomotion to assist with moving through the forest canopy – much like a fifth limb. This is fundamentally different from the way that capuchin monkeys use their tails because capuchins tend to brace themselves with their feet and tail (like a tripod) for stability while feeding on fruits at the ends of thin tree branches, but they do not use their tails while moving. And this basic distinction in the way the tail is used can be seen in specific anatomical differences between ateline and capuchin prehensile tails.





Friction pad on tail of mantled howling
monkey (Alouatta palliata) at Hacienda La Pacifica,
Guanacaste, Costa Rica, 2004.

Capuchin monkeys, like most other primates, have tails that are completely covered in hair. The skin underlying the hair is replete with slow-adapting pressure and touch receptors (Ruffini endings) that allow the animal to detect the position of the tree branch substrates during postural behaviors like sitting or lying down. The ateline monkeys, however, uniquely possess a hairless friction pad on the ventral (anterior) and distal (tip) of the tail. This friction pad senses touch and pressure with slow-adapting sensors like the skin of the capuchin tail, but it is also full of rapid-adapting sensors (Meissner’s and Pacinian corpuscles) that are useful for detecting the substrate during locomotion. Additionally, the ateline tail friction pad contains dermatoglyphics, or “finger” prints, similar to those found on fingers and toes. This pad, with its dermal ridges, provides the source of friction so that the tail does not slip during suspension and locomotion.


So, as you can see, if Curious George was actually a monkey, there is no question that he would be infinitely more interesting** because monkey tails are interesting. And if he were a New World monkey with a prehensile tail, I have no doubt his curiosity would get him into so many more pickles because he would have the ability to hang from his tail and manipulate things with his hands and feet. Unfortunately, for over 75 years George has been given credit for being a monkey, when all signs point to him being an ape – the biggest clue being that he does not have a tail.

*Ok… so almost all monkeys have tails. There is an interesting case of near taillessness in Macaca sylvanus, also called the Barbary macaque. These monkeys, who live in Gibraltar and constitute Europe’s only wild population of monkeys, have a vestigial, stumpy, soft tail – a bulbous nubbin. And although they have tail vertebrae like every other monkey, these vertebrae do not actually extend into the external tail at all, so they are more like the tailbone (coccyx) that apes have than those of a typical monkey tail. For this reason, Barbary macaques are mistakenly called Barbary apes. But they are not apes. They are monkeys – unlike Curious George.

**Tamping down the hyperbole for a moment, the truly most interesting aspect of George, given that he is not a monkey, is the history of how he came to be so beloved by so many. You can read this fascinating history here.

Contributed by: Jason Organ, Ph.D.
Tail Jason on Twitter.




Organ JM, Teaford MF, & Taylor AB (2009). Functional correlates of fiber architecture of the lateral caudal musculature in prehensile and nonprehensile tails of the platyrrhini (primates) and procyonidae (carnivora). Anatomical record (Hoboken, N.J. : 2007), 292 (6), 827-41 PMID: 19402068

Organ JM (2010). Structure and function of platyrrhine caudal vertebrae. Anatomical record (Hoboken, N.J. : 2007), 293 (4), 730-45 PMID: 20235328

Organ JM, Muchlinski MN, & Deane AS (2011). Mechanoreceptivity of prehensile tail skin varies between ateline and cebine primates. Anatomical record (Hoboken, N.J. : 2007), 294 (12), 2064-72 PMID: 22042733

Deane AS, Russo GA, Muchlinski MN, & Organ JM (2014). Caudal vertebral body articular surface morphology correlates with functional tail use in anthropoid primates. Journal of morphology, 275 (11), 1300-11 PMID: 24916635

Russo GA (2015). Postsacral vertebral morphology in relation to tail length among primates and other mammals. Anatomical record (Hoboken, N.J. : 2007), 298 (2), 354-75 PMID: 25132483