I’m a big fan of twitter. If you’re like me and follow the, err, very interesting @TakeThatDarwin account, you’ll see retweetings of all manner of wit and wisdom from creationists and other deniers of evolution. You know the sort of thing: second law of thermodynamics, monkeys monkeys monkeys. A persistent statement made by evolution deniers is the “If humans/apes evolved from monkeys, why are there still monkeys?” thing.
While it might be a fairly pointless exercise deconstructing the premise concerned, it might not, since I’m not sure that a satisfying amount of information on monkey and ape evolution is all that available (for free) online. With that in mind, here we go. There are pictures, and it might be good to see some of those pictures get used whenever the “why are there still monkeys” rhetoric is wheeled out yet again.
Let’s say upfront that asking “if humans/apes evolved from monkeys, why are there still monkeys?” is exactly the same as saying “if there are snakes, why are there still lizards?”, “if there are tetrapods, why are there still fish”, or “if there are European Americans, why are there still Europeans?”. The point that stubborn creationists apparently refuse to appreciate is that only one group among the animals that we call ‘monkeys’ evolved into the animals that we call ‘apes’: other ancestral monkeys begat more monkeys, and apes are, in fact, merely one monkey lineage among several. Yes, you should think of apes as big, weird monkeys. We just use a different name for that lineage of big weird monkeys because we find this distinction a useful one. This distinction would be less obvious if early, monkey-like members of the ape lineage still existed. But they don’t; they’re extinct. So you should think of apes as monkeys in the same way that birds are dinosaurs, snakes are lizards, and humans are apes.
The shape of the tree. Let’s look at all of this within the context of primate evolutionary history. First of all, some key terms. Monkeys and apes together – the so-called ‘higher primates’ – constitute Anthropoidea. Within Anthropoidea, Old World monkeys and apes form Catarrhini, the sister-group to Platyrrhini (the New World monkeys). Within Catarrhini, the ape lineage is Hominoidea, and the Old World monkey lineage is Cercopithecoidea. The adjacent labelled cladogram should help you out.
In recent years several new fossil anthropoids have been described that appear close to various of the key branching points in anthropoid phylogeny. Catopithecus from the Upper Eocene of Egypt is a stem-catarrhine close to the platyrrhine-catarrhine split, Saadanius from the Oligocene of Saudi Arabia must have been very close to the ancestry of the catarrhine clade that includes both apes as well as Old World monkeys, Nsungwepithecus appears to be a stem-member of the cercopithecoid clade, while Victoriapithecus from the Miocene of Kenya is an early Old World monkey outside the clade that includes colobines and cercopithecines.
Many other fossil taxa have been identified as stem-members of Anthropoidea, Catarrhini and Cercopithecoidea. In addition, several completely extinct anthropoid lineages existed during the Oligocene and Miocene, including the pliopithecoids and dendropithecids.
You, and all your friends, are monkeys. Because all of the fossil primates just mentioned fall somewhere on the tree between platyrrhines and Old World monkeys, all can be regarded as ‘fossil monkeys’, even though none of the taxa or groups I’ve just mentioned are members of modern lineages. And if we were to see any of these animals in life we would regard them as ‘monkeys’ with little hesitation.
My point here is that it’s clear that the term ‘monkey’ does not only apply to the members of two specific living anthropoid clades – Platyrrhini and Cercopithecoidea, respectively – it’s also a catch-all label for primates of a certain evolutionary grade: for ‘non-hominoid anthropoids’. But from an evolutionary, tree-based perspective, hominoids are just one monkey lineage among many. We humans, and all our other hominoid cousins, are – as I already said above – big, tail-less, bipedal monkeys. This concept might be familiar if you’re a regular Tet Zoo reader. And, look, there’s even merchandise…
Modern monkeys are mostly modern. If hominoids – apes – evolved from among a bunch of anthropoid primates that we call ‘monkeys’, then some non-hominoid monkeys really were ‘ape prototypes’. But the vast majority were not, and modern monkeys are clearly not, either. Here we return to that “if there are apes, why are there still monkeys?” fallacy. Because some monkeys gave rise to that one lineage that we call apes, some people seem inclined to regard all monkeys as ‘ape ancestors’. This is, of course, no more logical than thinking that, say, all fish should be regarded as ancestral to frogs and salamanders, or that all wolves are supposed to turn into domestic dogs.
Indeed, the modern monkey groups are far from being anachronistic relicts that should be regarded as hopeful ape prototypes. On the contrary, the living monkey groups are comparatively young, vigorous evolutionary radiations, the majority of their many branches only having diverged within the past 20 million years; many within the last 10 million years (Raum et al. 2005, Opazo et al. 2006, Hodgson et al. 2009, Meyer et al. 2011, Pozzi et al. 2014). And morphology, genetics, ecology, behaviour and biogeography all show that some monkey species groups are the products of bursts of evolution that occurred just within the last few million years (Li et al. 2009, Meyer et al. 2011). This is in particular obvious when we look at the riotous diversity within such monkey groups as the Cercopithecus guenons of western, central and eastern Africa – the recent, explosive evolution of which will be familiar to you if you follow the writings of Jonathan Kingdon (Kingdon 1986, 1990, 1997) – or the Presbytis leaf monkeys.
What’s even less widely appreciated is that these young, vigorous colobine and cercopithecine radiations have meant that monkeys have actually taken over roles that, previously, were occupied by small-bodied apes. Yes, that’s right, apes were partly occupying the ‘monkey role’ before modern monkeys were, and it’s now well known that apes in the past (the Miocene especially) were substantially more diverse, more abundant, more widespread, and more ecologically important back then than they are today. Studies on this Miocene ape diversity rarely fail to take advantage of the ‘Planet of the Apes’ angle, and in fact this very title has been used on a few occasions by fossil ape expert David Begun (2003, 2015).
The modern ape lineages – gibbons, orangs, gorillas, chimps and humans – are all unusual big-bodied habitat specialists compared to the majority of extinct hominoids. Ok, modern humans certainly aren’t habitat specialists, but our early evolution was wholly limited to savannah-woodland regions in eastern Africa.
What were monkeys doing at this time of extreme ape diversity? We should imagine small, plain, anatomically archaic monkeys living alongside Miocene apes but not really doing the sorts of things that monkeys do today. These archaic monkeys were not the often large, specialised, flamboyant, showy or spectacular monkeys of today. Geladas, drills, mandrills, baboons, patas monkeys, the biggest Asian and African colobids (like proboscis monkeys and black-and-white colobus monkeys) and the biggest platyrrhines (like muriquis, woolly monkeys and spider monkeys) are all sizeable primates that can reach or exceed 10 kg, and are often specialised for strong terrestriality or arboreality. Many are visually spectacular with manes, beards, prominent facial or snout markings, long, luxurious tails, and brightly coloured faces, genitals and rumps. My point is that much of this spectacular living monkey radiation – involving giant species and highly ornamented species – should be imagined as a new thing that mostly evolved within the last several million years. Monkeys have not always been like this.
So give it up on the dumb mis-characterisation of monkeys as ‘hopeful apes’ that don’t make sense within the context of evolution. The existence of monkeys – of non-hominoid anthropoids, the animals we call ‘monkeys’ – is no more a paradox than is the existence of fish alongside tetrapods, wolves alongside dogs, or snakes alongside lizards. And most monkeys are young – ‘new’, if you like – within a geological context.
Primates of several sorts have been covered on Tet Zoo before. See…
- Zihlman’s ‘pygmy chimpanzee hypothesis’
- Marmosets and tamarins: dwarfed monkeys of the South American tropics
- The amazing swimming Proboscis monkey (part I)
- Nasalis among the odd-nosed colobines or The “Nasalis Paradox” (proboscis monkeys part II)
- Old World monkeys of choice
- De Loys’ Ape and what to do with it
- Why Humans Are Important to Studies of Primate Diversity
- Piltdown Man and the Dualist Contention
- Piltdown Man Came from The Lost World... Well, No, It Didn't
Refs - -
Begun, D. R. 2003. Planet of the apes. Scientific American 289 (2), 64-73.
- . 2015. The Real Planet of the Apes: A New Story of Human Origins. Princeton University Press, Princeton.
Hodgson, J. A., Sterner, K. N., Matthews, L. J., Burrell, A. S., Jani, R. A., Raaum, R. L., Stewart, C.-B., Disotell, T. R. & Goodman, M. 2009. Successive radiations, not stasis, in the South American primate fauna. Proceedings of the National Academy of Sciences of the United States of America 106, 5534-5539.
Kingdon, J. 1986. An embarrassment of monkeys. BBC Wildlife 4 (2), 52-57.
- . 1990. Island Africa: the Evolution of Africa’s Rare Animals and Plants. Collins, London.
- . 1997. The Kingdon Field Guide to African Mammals. Academic Press, San Diego.
Li, J., Han, K., Xing, J., Kim, H.-S., Rogers, J., Ryder, O. A., Disotell, T., Yue, B. & Batzer, M. A. 2009. Phylogeny of the macaques (Cercopithecidae: Macaca) based on Alu elements. Gene 488, 242-249.
Meyer, D., Rinaldi, I. D., Ramlee, H., Perwitasari-Farajallah, D., Hodges, J. K. & Roos, C. 2011. Mitochondrial phylogeny of leaf monkeys (genus Presbytis, Eschscholtz, 1821) with implications for taxonomy and conservation. Molecular Phylogenetics and Evolution 59, 311-319.
Opazo, J. C., Wildman, D. E., Prychitko, T., Johnson, R. M. & Goodman, M. 2006. Phylogenetic relationships and divergence times among New World monkeys (Platyrrhini, Primates). Molecular Phylogenetics and Evolution 40, 274-280.
Pozzi, L., Hodgson, J. A., Burrell, A. S. Sterner, K. N., Raaum, R. L. & Disotell, T. R. 2014. Catarrhine primate divergence dates estimated from complete mitochondrial genomes: concordance with fossil and nuclear DNA evidence. Molecular Phylogenetics and Evolution 75, 165-183.
Raaum, R. L., Sterner, K. N., Noviello, C. M., Stewart, C. B. & Disotell, T. R. 2005. Catarrhine primate divergence dates estimated from complete mitochondrial genomes: concordance with fossil and nuclear DNA evidence. Journal of Human Evolution 48, 237-257.