When I recently reviewed The Real Planet of the Apes, I casually wrote how that book dealt with the evolution of Old Work monkeys and apes, ignoring New World monkeys which went off on their own evolutionary experiment in South America. But that did leave me wondering. Those New World monkeys, what did they get up to then? Here, primatologist Alfred L. Rosenberger provides a comprehensive and incredibly accessible book that showed these monkeys to be far more fascinating than I imagined.

New World Monkeys: The Evolutionary Odyssey, written by Alfred L. Rosenberger, published by Princeton University Press in September 2020 (hardback, 350 pages)

Most people are probably not very familiar with these monkeys. Technically known as platyrrhines, they are predominantly arboreal (i.e. living in trees), small to medium-sized primates. You might know the insanely loud howler monkeys from nature documentaries. Perhaps you have heard of capuchin monkeys or spider monkeys. But you could be forgiven for not having heard of marmosets and tamarins, or the even more obscurely named titis, sakis, and uacaris. A total of 16 genera are recognized, but outside of the scientific literature and abovementioned technical books, these monkeys are not all that well known. And that is a shame as, from an evolutionary perspective, this is a unique group.

Now, before Rosenberger gets to this, it helps to better know these monkeys. Accompanied by many excellent illustrations and photos, the first half of New World Monkeys is dedicated to their ecology, behaviour, and morphology. Topics covered include their diet and dentition; locomotion and the anatomy of hands, feet, and prehensile tails; but also brain size and shape; and their social organization and ways of communicating via sight, sound, and smell.

The platyrrhines are a diverse bunch with some remarkable specialisations. In the family Cebidae we find the smallest members, some of whom, the Marmosets and Pygmy Marmosets, have teeth specialized for gouging the bark of gum trees and feeding on the gum that is released in response. In the family Pitheciidae we find the only nocturnal member, the Owl Monkeys, which have concomitant morphological adaptations such as enlarged eyes. In both this and the closely related Titi Monkeys, individuals have the adorable habit of twining their tails when e.g. socializing or sleeping. The family Atelidae is home to species with exceptionally prehensile tails whose underside ends in a pad with a fingertip-like surface. The Muriquis and the aptly-named Spider Monkeys use them as a fifth limb in locomotion, as demonstrated by a striking photo of a Black-faced Spider Monkey on plate 13. Here we also find the well-known Howler Monkeys, whose skull is heavily modified to support the exceptionally loud vocal organs in their throat and neck.

“[…] the whole radiation has been remarkably stable for at least 20 million years. Today’s New World monkeys are virtually unchanged from their ancestors […] This stands in sharp contrast to the evolutionary history of Old World monkeys […]”

Despite these differences, platyrrhines are closely related and form what is called an adaptive radiation. Just like the textbook example of Darwin’s finches, many members have evolved unique adaptations and ways of living to minimise competition and maximise resource partitioning. Two ideas feature prominently in this book to explain how platyrrhines have evolved and what makes this adaptive radiation both so diverse and so interesting.

One idea is what Rosenberger calls the Ecophylogenetics Hypothesis. If I have understood him correctly, this combines information on a species’s ecology and phylogeny, its evolutionary relationships. It can offer hypotheses on how ecological interactions have evolved, but it also recognizes that ecological adaptations are shaped and constrained by evolutionary relatedness. For the platyrrhines, taxonomically related members are also ecologically similar. To quote Rosenberger: “[…] phylogenetic relatedness literally breeds resemblance in form, ecology, and behavior” (p. 96) and “Each of the major taxonomic groups that we define phylogenetically is also an ecological unit […]” (p. 97).

The other idea that makes the platyrrhines so interesting is dubbed the Long-Lineage Hypothesis. An extensive chapter on the fossil record documents how the whole radiation has been remarkably stable for at least 20 million years. Today’s New World monkeys are virtually unchanged from their ancestors, living the same lifestyles and occupying the same ecological niches. Some fossils have even been classified in the same genus as their living counterparts. This stands in sharp contrast to the evolutionary history of Old World monkeys where there has been a constant churn, whole groups of primates evolving and going extinct with time.

“Without ever losing academic rigour or intellectual depth, Rosenberger quietly proves himself to be a natural-born teacher and storyteller […]”

What stands out, especially when Rosenberger starts talking taxonomy and evolution, is how well-written and accessible the material here is. He takes his time to enlighten you on the history, utility, and inner workings of zoological nomenclature, making the observation that “names can reflect evolutionary hypotheses“. Here, finally, I read clear explanations of terms such as incertae sedis (of uncertain taxonomic placement), monotypic genera (a genus consisting of only a single species), or neotypes (a replacement type specimen). Similarly, there are carefully wrapped lessons on how science is done—on the distinction between scenarios and hypotheses, or how parsimony and explanatory efficiency are important when formulating hypotheses. Without ever losing academic rigour or intellectual depth, Rosenberger quietly proves himself to be a natural-born teacher and storyteller, seamlessly blending in the occasional amusing anecdote.

A final two short chapters conclude the book. One draws on the very interesting question of biogeography, i.e. on how platyrrhine ancestors ended up in South America, which was long an island continent. Rosenberger convincingly argues against the popular notion of monkeys crossing the Atlantic on rafts of vegetation* and in favour of more gradual overland dispersal. The other chapter highlights their conservation plight as much of their tropical forest habitat has been destroyed by humans.

With New World Monkeys, Rosenberger draws on his 50+ years of professional experience to authoritatively synthesize a large body of literature. As such, this book is invaluable to primatologists and evolutionary biologists and should be the first port of call for anyone wanting to find out more about the origins, evolution, and behaviour of these South and Central American primates.

* One mechanism that Rosenberger does not mention is that tsunamis could be behind transoceanic rafting, as argued in a recent Science paper. This looked at marine species in particular and I doubt it would make much of a difference for terrestrial species. Most of the objections Rosenberger gives would still apply.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

New World Monkeys

Other recommended books mentioned in this review:

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Charismatic as big cats might be, their origins and evolutionary history are still not fully understood. In a mind-bogglingly beautiful marriage of art and science, On the Prowl provides a current overview of big cat evolution that will have many a book lover purring with pleasure.

On the Prowl: In Search of Big Cat Origins, written by Mark Hallett and John M. Harris, published by Columbia University Press in June 2020 (hardback, 259 pages)

Before I even get to the contents of the book I simply have to first highlight the artwork. On the Prowl is authored by naturalist and scientific artist Mark Hallett and geologist and emeritus curator John M. Harris, with Hallett additionally providing artwork. And these are not mere pretty decorations.

Oh my, where do I even begin?

This is the rare category of tastefully executed scientific illustrations: anatomical drawings, behavioural sequences, phylogenetic trees, maps, reconstructions of life appearance, and beautiful full-bleed (i.e. printed edge-to-edge) pictures opening each chapter. Every drawing, full of detail, has been carefully crafted, has a function in the book, and has been drawn in the same tasteful pencil-sketch style. Jaw-dropping? Gob-smacking? You pick your favourite superlative—I was floored when I first opened this book. Basically, do not browse through this if you were planning not to buy more books this month, because it will be very hard to put it back down.

But what of the actual writing? On the Prowl spends five chapters tracing the outline of big cat evolution during the last 23 million years. The last three chapters deal, notably, with recent declines and extinctions, and current conservation concerns. The focus here is on the pantherines or subfamily Pantherinae; the lions, tigers, jaguars, leopards, and snow leopards. Not discussed in as much detail and acting more as supporting cast are the Felinae (pumas, cheetahs, and smaller genera such as lynxes, ocelots, clouded leopards etc.) and the various sabertoothed cats. Seeing the number of books already dealing with these (Anton’s Sabertooth and the two edited collections from Johns Hopkins University Press) it is easy to agree with their decision not to focus any further on sabertooths here.

“I simply have to first highlight the artwork […] This is the rare category of tastefully executed scientific illustrations […] I was floored when I first opened this book”

The story of pantherine evolution is far from fully resolved, and this part of the book required close attention and occasional rereading. The various lineages and subspecies, notable fossil finds, and competing hypotheses all make for a rather complicated story full of details. I should add that I am not faulting Hallett and Harris’s writing, as they do an admirable job distilling a lot of technical literature into a very readable book. It is simply that, much as we might like a good narrative, reality is often unruly and does not yield to a clean, neat story. Biology is messy like that. But what a story it nevertheless is!

An introductory overview gets you up to speed on early carnivore and carnivoran evolution and explains the difference between the two. The first cat-like species you then meet is the genus Proailurus, which (likely) evolved into Pseudalaerus, the potential ancestor to all the big cats and the “true” sabertooth cats (the machairodontines, which includes the famous Smilodon). At the time, these faced stiff competition from the so-called “false” sabertooth cats, the nimravids and barbourofelids.

Personal revelation number one: I was ignorant of the fact that not all sabertooths are closely related (had I actually read Mauricio Anton’s Sabertooth, I would know all this). The family Nimravidae arose very early, some 50 million years ago, and is technically merely a cat-like carnivore. The subfamily Machairodontinae split off from the cat family Felidae some 16 million years ago and is technically a true cat. Despite this taxonomical distance, they came to closely resemble each other. (Whoever said that what looks like a duck and quacks like a duck, probably is a duck never heard of convergent evolution…).

“it is starting to look that the Tibetan Plateau was ground zero for the pantherines from which both the snow leopard–tiger and the jaguar–lion–leopard lineages dispersed globally.”

What probably gave the Felidae the competitive edge was changes in climate and, with it, vegetation: closed forests gave way to open woodlands and savannas. Chapter 2 describes in marvellously illustrated detail the anatomical and behavioural adaptations of the pantherines that made them such formidable hunters in these open habitats and helped them claw their way to the top. This placement of big cat evolution in the context of their ecosystems and their relationship to other animals is a recurring and very welcome theme in this book. The earliest known pantherine we then meet is Panthera blytheae, a possible ancestor of the modern snow leopard, which brings me to…

Personal revelation number two: it is starting to look that the Tibetan plateau was ground zero for the pantherines from which both the snow leopard–tiger and the jaguar–lion–leopard lineages dispersed globally. Two appendices give an illustrated overview of felids in geologic time and pantherin dispersal across the world. These are useful, but, like executive summaries, are very condensed. I would have loved a few more detailed illustrations of the various timelines over which this happened, breaking out the individual lineages.

Now, connoisseurs might have immediately perked up their ears when hearing of this book. How does it compare to the 1997 book The Big Cats and their Fossil Relatives? This was, incidentally, also published by Columbia University Press, and similarly combined beautiful artwork with accessible text. It is one of the first things the authors tackle, writing that it focused more on the true felid and the nimravid cats, and comparing the books indeed confirms this. I can see two reasons why owners of the 1997 book want to pick up this one as well. One is that it fills you in on the intervening 23 years of scientific research, especially that coming out of the Asian palaeontology community. Panthera blytheae was only discovered in 2010, and pinpointing the Tibetan Plateau as the centre of pantherine radiation strikes me as a significant advance in our understanding. Two, On the Prowl spends a substantial chunk dealing with both recent extinctions and conservation concerns, something that the previous book mentioned only briefly at the end.

“Having told the story of big cat evolution, it would have been an oversight to turn a blind eye to the massive losses caused by human greed and cruelty.”

Having told the story of big cat evolution, it would have been an oversight to turn a blind eye to the massive losses caused by human greed and cruelty. Thus, these chapters and their no-punches-pulled tone are fully justified. One chapter focuses on the early decline following the last ice age, in particular discussing the decline of the steppe lion (of the four discussed extinction scenarios, only one involves humans). I was somewhat surprised to see only minimal mention of Paul Martin’s overkill hypothesis when drawing a comparison to the fate of the American lion, Panthera atrox, and no mention at all of End of the Megafauna that critically discussed it. A second chapter picks up the story of extinction with the slaughter of big cats in Roman amphitheatres and habitat destruction ever since agriculture took off some ten thousand years ago. It also prominently mentions the huge impact of trophy hunting by western colonialists in Africa and Asia. The last chapter highlights the ongoing threats of poaching and wildlife trafficking (particularly slamming tiger farms in China and the canned lion hunting industry in Africa), human-wildlife conflict between carnivores and cattle herders, the shortcomings of national parks, and reasonable and critical consideration of future options such as captive breeding, rewilding, and de-extinction.

Overall, On the Prowl provides a superb overview of the complex and rich story of big cat evolution, while being an outstanding showcase of how beautiful artwork can support science communication. I have no hesitation to recommend this book as one of 2020’s must-buy palaeontology books.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

On the Prowl

Other recommended books mentioned in this review:

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“Poached: Inside the Dark World of Wildlife Trafficking“, written by Rachel Love Nuwer, published in Europe by Scribe Publications in September 2018 (paperback, 374 pages)

Of all the victims of wildlife trafficking, elephants are probably the most well-known. Their ivory tusks have long been a desirable material that is turned into carvings and trinkets. Conservationist Richard Leakey got this topic into the public consciousness by convincing the Kenyan president to command the public burning of a large pile of confiscated ivory in 1989 (see Wildlife Wars: My Battle to Save Kenya’s Elephants). Ever since, conservationists have been fighting an uphill struggle in Africa that continues to this day (see for example Ivory, Horn and Blood: Behind the Elephant and Rhinoceros Poaching Crisis and Ivory: Power and Poaching in Africa).

But it is not just Africa, and it is not just elephants. Poached is an incredible, globe-trotting tour that must have cost Nuwer dearly in both time and money (not to mention sanity, seeing some of the cruelty she has witnessed). She tramps around Vietnam where pangolins (scaly anteaters) are being poached for their meat and scales, neighbouring Laos, where tigers are being farmed illegally for all sorts of body parts, Indonesia, where rare reptiles are being caught for the pet trade, and China, where bears are being kept in cages and “milked” for bile. In Africa, it is rhinos that are being targeted for their horns, and various big cats that are hunted for trophies. And these are just the notable flagship species. For others, like the vaquita, it takes the hard work of other journalists to highlight their plight (see my review of Vaquita: Science, Politics, and Crime in the Sea of Cortez and my interview with the author).

One of the many problems is that, although an international treaty called CITES exists that seeks to regulate the illegal trade, many species are not listed because we know virtually nothing about them or the status and health of their populations. But that does not stop the illegal trade. Nuwer sits in on one of their meetings where member states negotiate the level of protection granted to various species and witnesses first-hand the haggling and negotiating. If the slow progress at these meetings isn’t frustrating enough, there is very little in the way of power to enforce the decisions taken here. Countries can and do simply ignore them.

“Poached is an incredible, globe-trotting tour that must have cost Nuwer dearly in both time and money (not to mention sanity, seeing some of the cruelty she has witnessed)”

Corruption runs like a red thread through this story. From airport employees and border guards, all the way up to government officials and even heads of state – the illegal trade in wildlife is so profitable that many have no qualms turning a blind eye in exchange for money. Despite much public lip-service and promises to protect species and crack down on smuggling, little to no progress is made on the ground.

Nuwer puts herself in dangerous situations more than once during the course of her investigations – nosy journalists have faced intimidation, violence, and sometimes even death. Though I do not want to downplay the risks she has taken, it is remarkable how willing some people are to openly talk to her, whether they be poachers, middle-men in the supply chain, restaurant owners selling exotic meat such as snake, pangolin or civet, or other end users. It is another clear sign that there is virtually no law and order in many countries. These conversations are eye-opening, revealing a completely different worldview and mindset compared to conservationists. Poachers are often aware of the harm they are inflicting and see populations in the field crashing, but quote poverty and hardship to justify their choices. Further up the chain, plain greed and indifference often dominate.

Particularly troublesome are the superstitions that accompany traditional medicine, especially in Asia. No matter how often you show that rhino horn cannot cure cancer, or that tiger bones ground into paste do not alleviate aching joints, the placebo effect is powerful. Worse, even where synthetic or farmed alternatives are available, many people choose to believe that parts from wild-caught animals are imbued with natural vigour, so they will still preferentially obtain these. Ironic, as in some cases the natural substances are polluted, impure, or so soaked in stress hormones and physiological metabolites that they cause poisoning.

“Particularly troublesome are the superstitions that accompany traditional medicine […] No matter how often you show that rhino horn cannot cure cancer, or that tiger bones ground into paste do not alleviate aching joints, the placebo effect is powerful”

Are there solutions? Nuwer frequently quotes from Felbab-Brown’s book The Extinction Market: Wildlife Trafficking and How to Counter It that was published around the same time (this looks at lessons learned from the fight against the global drug trade – sounds very interesting, though I have not read it yet) and explores some solutions herself. This includes widely praised campaigns of dedicated individuals such as Jill Robinson who gives public talks on the horrors of bear bile farms. But Nuwer also talks to game ranchers in South Africa whose questionable approach to conservation takes the form of monetising farmed animals such as rhinos and lions to supply a legal and regulated trade. An example of the latter is the recent scandal around Cecil the lion, who was shot by an American big-game hunter who paid a small fortune for the “privilege” – money that ranchers invest as much in wildlife protection as in their own bottom line.

With Poached, Nuwer covers a large number of topics. The scope of her coverage is both impressive and depressing. This book does not make for comfortable reading, but it is an important story that needs telling. Nuwer remains remarkably cool and non-judgemental, even in the face of corruption, cruelty, and callousness. Fervent animal lovers might struggle with this, but Nuwer convincingly shows just how complex and multi-faceted this problem is, how many cultural divides it crosses. I believe her approach is probably the best to try and win as many hearts as possible to her cause.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Poached paperback, hardback, ebook, audiobook or audio CD

Other recommended books mentioned in this review:

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