Online at: http://politicalaffairs.net/article/articleview/3347/1/165

Book Review: The Hunt for the Dawn Monkey

By Thomas Riggins

Archives - Dates and Topics

2006 – online

May – June 2006

May 1 – May 7 click here for related stories: science

5-02-06, 10:08 am

The Hunt for the Dawn Monkey: Unearthing the Origins of Monkeys, Apes, and Humans

Chris Beard
University of California Press, 2004

The progressive community can breathe a little easier with the roll back, for the time being, of the antievolutionary religious diehards who have recently caused so much trouble in Kansas and Pennsylvania. Now that the latest round seems to have gone to Darwin and science, it might be a propitious time to review just what our evolutionary status is.

That we have all evolved from the monkeys is not a new thought for Marxists. When Darwin first suggested this with the publication in 1859 of The Origin of Species Marx and Engels were quick to give their support to his ideas. They hailed his book as a great scientific advance. A few years later Engels wrote about human origins himself, in an unfinished essay called "The Part Played by Labour in the Transition from Ape to Man" and now included in his The Dialectics of Nature.

What Engels had to say, while technically out of date, is not so far off the mark as many people might think. For example, in Engels’ day the Earth was thought to be about 100 or so million years old not the 4.5 billion years we think today. Thus Engels’ writes:

Many hundreds of thousands of years ago, during an epoch,
not yet definitely determinable,... the Tertiary period... a particularly highly-developed race of anthropoid apes lived somewhere in the tropical zone-- probably on a great continent that has now sunk to the bottom of the Indian Ocean..... They were completely covered with hair, they had beards and pointed ears, and they lived in bands in the trees.

German (in which Engels wrote) uses the same word for "monkey" and "ape." Engels is basing himself on Darwin and is describing the early anthropoid ancestors of what we now know to be the great apes and humans. The Tertiary period is today measured in millions not hundreds of thousands years, and there is no lost continent on the bottom of the Indian Ocean. Engels wrote before we knew about continental drift. These bands did live in a tropical environment only it was in Asia, more specifically in places such as China and neighboring areas.

Engels further says that "Hundreds of thousands of years.... certainly elapsed before human society arose out of a troupe of tree climbing monkeys. Engels’ is correct if we substitute "tens of millions" for his "hundreds of thousands." Engels was definitely on the right tract, but we have learned a great deal more about this monkey troupe, these dawn monkeys, since the 1870s when his essay was written. It would be nice to have some updated information.

This has been done for us by Chris Beard notably the winner of a MacArthur "genius grant" but who makes his living by being the curator of vertebrate paleontology at the Carnegie Museum of Natural History.

The vertebrates he is especially interested in are us, or more particularly our relatives and fellow primates the apes and monkeys-- both the quick and the dead. His book is a well written, minimally technical, popular account of the most recent discoveries, many made by Dr. Beard himself, and theories concerning our origins and evolutionary development.

What we want to know is, who are these "dawn monkeys" and what have they it to do with us? Early on we are informed that "virtually all paleoanthropologists" believe that the lineage leading to humans developed in Africa between five and seven million years ago. It was in this two million year fuzzy time period, between the 7 and 5, that the animals that eventually became us split off from the common ancestor that we share with the chimpanzees. In other words J. Fred Muggs and President Reagan had the same great, great, etc., for many more greats, grandparents (as do we all).

Beard is interested in pushing back the knowledge of our origins to even more remote time periods. If human primates diverged from apes, where did those apes come from? Have we found enough fossils to answer this question? Not only the "where" question but how long ago as well-- certainly the apes and their ancestors must have developed many millions of years before we and the chimpanzees separated and went our different ways.

A little time perspective is needed here. The dominance of the Age of Dinosaurs ended about 65 million years ago (mya) at the end of the geologic period called the Mesozoic. The period called the Cenozoic (Recent Life ) then began. This period is divided into seven divisions: the Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, and Holocene. The Eocene (dawn period) beginning about 55 mya and lasting until about 35 mya is where we are headed, incidentally, as the name of Beard’s book indicates.

There are around 35 species of living primates and the Eocene fossil primates mostly look like the "primitive" primates of today (the prosimians). But today we also have a group that, since it includes us, we like to call the "higher primates"-- these are the "anthropoids" and includes the monkeys, apes, and humans.

Now since we humans came from the apes, we have found that the apes came from the monkeys, so if we find the earliest monkey, that is if we find the earliest anthropoid we will push our family tree back to that point. Beard writes, "one of the most controversial issues in paleoanthropology today is how, when, and where the first anthropoids-- the common ancestors of monkeys, apes, and people-- evolved."

Beard has a "bold new hypothesis," based on recent fossil discoveries he has made in China, that will upset the hitherto existing scientific consensus regarding anthropoid origins. His theory moves the origin of the anthropoids from Africa to Asia and adds tens of millions of years to the age of this lineage. These new ideas all depend on the fossils Beard has called "the dawn monkey" (Eosimias) and how they are to be interpreted.

It appears that it won’t be an easy task that Beard has set himself since, as he says, for "the past several decades, all undisputed early anthropoids had been discovered in Africa" mostly due to the work of Dr. Elwyn Simons of Duke University working in the Fayum oasis in Egypt. So, a revolutionary new paradigm is afoot!

Beard says that his views are in the minority (this is because all new theories start out this way) but he gives three solid reasons to support his views. First, there is a small prosimian (pre-monkey like primate such as the lemur of today) known as a tarsier which seems to be closest in evolution to the first anthropoids. Beard thinks that their geological range points to an Asian origin for the first anthropoids. Based on the most recent DNA evidence he concludes that "the simplest hypothesis requires us to view tarsiers and anthropoids as descendants of a common ancestor." No tarsier or tarsier relatives "have ever been found in Africa. Second, there are fossils from Burma, found decades ago, which appear to be primitive anthropoids, and finally, Beard’s own discovery of Eosimias in China which he says is definitely a primitive anthropoid and is older than any African anthropoid discovery(except for one, as we shall see)..

The African anthropoids date from the next geological era, the Oligocene, while Eosimias dates from the Eocene era, many millions of years earlier. The dawn monkey’s remains show that it is intermediate between the prosimians of today and the modern monkeys. It is thus a real candidate as the ancestor of all modern anthropoids-- i.e., all living monkeys, apes, and humans.

After several chapters in which Beard discusses the ways in which primate fossils are classified and also their distribution in Asia, Europe, North America and Africa, he concludes that the AfricanOligocene anthropoid remains are too modern to represent the originating ancestors of modern anthropoids. Therefore we "have no choice but to plunge back into the mysterious void known as the Eocene." The void is "mysterious" because of the paucity of primate fossils in this era as compared with the Oligocene. Nevertheless, if the Oligocene remains are too advanced to represent transitional forms between the prosimians and the anthropoids, then it is to the Eocene that we must turn to look for such transitional forms. Here we should be mindful of a basic evolutionary rule, namely, "that similar features indicate descent from a common ancestor." This is a rule not a law but, except for examples of convergent and parallel evolution, it generally holds.

In two very interesting chapters ("Received Wisdom" and "The Birth of a Ghost Linage"), Beard discusses three of the most influential theories of anthropoid origins as well as more techniques used by paleontologists and paleoanthropologists in sorting out and classifying fossils. This is all very interesting and very nontechnical. A "ghost lineage" is a hypothetical set of fossils that should be intermediate between a "primitive" and an "advanced" form. This lineage gives us some idea of what we should expect to find in the deduction is correct. If we find such fossils-- very good-- it is evidence that our theory may be correct.

Beard claims that the tarsiers and the ur-anthropoids (ur= first) branched off from each other (that is from a common ancestor) at least 50 million years ago. So he needs to construct a ghost linage-- say from some early tarsier like creature to the Oligocene type monkeys and then see if he can find a fossil to verify the lineage. This is where Eosimias comes in.

It was in China that Beard and his associates and Chinese paleoanthropologists all working together came upon the fossil remains of a small marmoset sized primate with the distinctly hypostisized anthropoid characteristics they were on the lookout for. The remains predated the oldest African remains from the Fayum by at least 10 million years.

Beard waxes, I think, a little too poetically over this discovery:

China’s historic role as the cradle of one of the world’s great and enduring civilizations might now be extended tens of millions of years back in time, to an interval when the earliest members of the most diverse and successful branch of modern primates-- the anthropoids-- were just beginning to evolve the diagnostic features (like bigger brains, robustly constructed jaws, and associated changes in behavior and ecology) that would ensure their biological success.

In the world of the Eocene, when Africa, Europe, Asia, and India were separated from one another by water, the world of 50 million years ago, it doesn’t make much sense to talk of "China." Be that as it may, in today’s world, Chinese scientists can be proud of the essential role they played in this discovery-- which was actually made by Chinese members of the team.

Beard’s theory, however compelling, was not supported by a sufficient range of fossil evidence to convince the majority of scientists working in this field. Therefore, after its initial presentation, he and his collaborators and Chinese associates spent four years doing intensive field work in China. The result of this activity was the discovery of many new fossil primates, including anthropoids and different species of Eosimias. Now Beard had the evidence he needed to shore up his hypothesis of anthropoid origins.

"Our knowledge of Eosimias-- an animal that I had only recently ushered onto the scientific stage," he writes, "had improved rapidly and immensely. Eosimias had been introduced to the paleoanthropological community as a humble waif of a fossil whose claim to anthropoid status dangled by the thread of two scrappy jaws. Now, its place near the base of the great anthropoid branch of the primate family tree rested on a firm anatomical foundation.... No other fossil bearing on the very root of the anthropoid family tree can marshal such an extensive litany of anatomical features to support its pivotal evolutionary position."

This information, according to Beard, overthrows the heretofore established orthodoxy regarding the origin of the anthropoid line. The orthodox theory, based on the theories of Le Gros Clarke a generation ago, held that that the anthropoid line (and the hominid line eventually arising out of it) arose in Africa some 34 million years ago at the Eocene/Oligocene border. The ancestral ape that gave rise to gorillas, chimpanzees and humans dates from the Miocene, the next geological age. Beard’s evidence, however, transplants the origin of anthropoids in both time and place: to the Paleocene/Eocene border around 55 million years ago-- 20 million years earlier than previously thought. Now that several species of Eosimias have subsequently been discovered, Beard can confidently assert that eosimiids are "the most primitive anthropoids currently known."

Nevertheless, we should remember that while our ancestors originated in Asia, these "Asian anthropoids remained persistently primitive, while their African relatives evolved into increasingly advanced species" including us.

Now there is a fly in this ointment. Namely, the remains of an even older anthropoid than Eosimias have been found in Morocco. This is Altiatlasius koulchii from the Paleocene. How can Beard maintain that anthropoids originated in Asia if the oldest anthropoid remains ever discovered (Altiatlasius) are actually from Africa? The chapter "Into the African Melting Pot" deals with this problem. The short answer is that primitive anthropoids migrated from Asia to Africa earlier, by a factor of millions of years, than anyone had previously thought. Beard bases this on the fact that while Asia can show the development of the anthropoid line from the split with a common ancestor of the tarsiers, i.e., out of a tarsiod line, Africa not only doesn’t have any fossil tarsiers, it doesn’t have any primates at all antecedent to Altiatlasius. "Accordingly, Altiatlasius does not indicate that anthropoids originated in Africa. Rather, it signals that Asian anthropoids arrived there at a surprisingly early date."

Beard’s last chapter ("Paleoanthropology and Pithecophobia") reminds us that even though the anthropoids may have arisen first in Asia, our own branch of the anthropoid line has distinctly African origins. In this chapter the author recounts the history, basically in the early 20th Century, of trying to prove that humans evolved independently of the great apes, the early culmination if you will of the African anthropoids.

Because of DNA analysis the scientific consensus today is that humans and chimpanzees branched off from a common ancestor about seven million years ago. This would be just around the Miocene/Pliocene border-- the Pliocene would have begun about five or six mya and ended about 1mya with the start of the Pleistocene.

All of the early 20th Century programs to establish a non-ape ancestor for humans, Beard points out, were mostly motivated by racism, commitments to theories of eugenics, religious prejudices, and human arrogance. In a final coda Beard laments the fact that "pithecophobia" is still a force to be reckoned with. He suggests it may be behind the continuing human attitude of absolute superiority to and difference from all other animals. One of negative attitudes resulting from this is that there are not enough serious attempts being made to prevent the extinction of gorillas and chimpanzees in the wild (their numbers have declined by 50% in the last 20 years-- mostly killed by humans for the "bushmeat" trade). I will quote Beard’s parting words: "Humanity as a whole is embedded within a rich biological tapestry. The living legacy of that common evolutionary journey deserves to be celebrated rather than despised. Pithecophobia in all of its manifestations conflicts with our own deep roots."

--Thomas Riggins is the book review editor of Political Affairs and can be reached at pabooks@politicalaffairs.net

| Send to friend |