Niles Eldredge - The Darwin Blogs

The Darwin Blogs – January 28, 2007.

Galapagos Blog # 3

January 25, 2007

My Dear Eldredge—

It was a delightful experience to read your previous Galapagos Blog, wherein you describe in some detail the effects of the current (yet I am to understand unequally distributed) rainfall about the islands. Well do I recall the scarce presence of water on most of the islands—leading me in one instance to rush across the characteristically harsh terrain in the mistaken belief that the little lake before me should prove to contain a reservoir of fresh water. A bitter disappointment it was to learn otherwise! Captain FitzRoy was obliged to return to the waterfall we had heard report of several years earlier, whilst the Beagle sojourned about the Falkland Islands—the waterfall cascading to the sea at Fresh Water Bay on the southeastern shore of Chatham Island. The seas were rough when first we sailed by, and hence the Captain wisely decided to seek to replenish the ship's store of water (for our long journey across the Pacifick) from some other source on the Galapagos—placing the crew on half rations until such a source could be located. That alternative source of water never materialised.

It is a source of no little distress that I may, in some small measure, have been a Culprit in the subsequent demise of both land iguanas and tortoises on James Island. Though I feel confident that you are not mistaken that it was ultimately the introduction of goats and pigs (and, no doubt, other foreign scourges—such as rats, cats, dogs & etc, etc) onto this (and other) islands that yielded the actual source of extinction working upon these native Species, I do confess that we visitors—and here I do count myself among them—experience no compunction whatsoever in seizing any thing we deemed eatable for our cooking pots. For it appeared to us that these native Species flourished in such Abundance that their supply should prove inexhaustible; I suppose every one finding himself in such circumstances would believe that the taking of just one or two of this or that should in itself cause little harm—turning a blind eye to the certainty that the numbers of visitors in search of Sustenance quickly add up—and pose an enormous threat to the native Species of each Island so exploited.

By the bye, yet another minor correction: I believe, upon examining my various accounts of my sojourn in the Galapagos, that you will discover that I passed but 9 days (of the 19 total days I spent ashore on the four Islands I visited in the Galapagos) on James Island—i.e. not the "15 days" you record in your previous blog.

That human predation—abetted by the destructive actions of goats, pigs and the like (who either competed for food resources—or themselves simply consumed—individuals of the local Species)—has proven to be the cause of extinction of some varieties or Species of indigenous animals on sundry Galapagos Islands, agrees rather well with the supposition I entertained virtually throughout my lifetime, viz: that extinction most often (if indeed not invariably) comes through the Agency of one or more other living Species. This position I recall having taken perhaps most decisively, for example, in my On the Origin of Species by Means of Natural Selection, though in that instance I had in mind largely the competitive threat to the continued existence of older Species posed by their superior, newly evolved descendant Species (their collateral kin, as it were), who might be anticipated to prevail more efficiently in the Struggle for Existence than their older relations—and hence might drive the latter to the oblivion of Extinction.

I had come to the view that Extinction is often a matter of the superior, more highly evolved driving out the older, less well-endowed species only after careful consideration of alternative views. Mr. Lyell, for example, insisted that Species persist for an appointed time, but eventually are removed through the Agency of physickal changes in their circumstances. I well remember puzzling over his views on extinction as I contemplated the demise—in near-recent times—of the large mammals I discovered as fossils in the Fall of 1832 at Bahia Blanca (and subsequently at other places—though never again in such great numbers of individuals or Species). The modern guanacos, armadillos and rheas thrive on the sparse, dry plains of Patagonia—and my examination of the rocks in which the fossils of extinct forms (some—as in the case of the glyptodont as identified upon my subsequent return home by Mr. Owen—clearly allied to Species currently alive—armadillos in the case of the glyptodont) convinced me that the conditions under which the Extinct fauna lived were very like those conditions still obtaining in Patagonia. In short, I could see no cause for attributing their Extinction to a change in their physickal circumstance.

I did, for a brief period both whilst on the Beagle, and even for a short while following my return to London in 1836, entertain the notion that perhaps each Species has its own innate life span (rather like that of an individual Human Being—unless cut short by accident, etc etc)—but by the time I opened my "Transmutation Notebooks" I had come round to the view that it is mostly a matter of competition—or predation—by other Species that most often is the cause for Extinction. Thus did I return to the view of Mr. Lyell that external causes are to blame for extinction—though I saw such causes as predominantly biological, not physickal as Mr. Lyell always insisted upon.

Your trip must nearly be drawing to a close. I do hope for at least one more Report on your adventures in the Galapagos.

Once again, allow me to assure you, Eldredge, how much pleasure I have gained by your first-hand observations of the Islands that played so important a part in the forming of my Views—Islands which, on many occasions, I regretted not having been able to have explored longer—or have been more assiduous in the collecting of its Inhabitants (though I did collect every specimen of every plant species I encountered on the four Islands that I did manage to visit).

Yrs. Sincerely,

Ch. Darwin

PS: And, oh yes, Poor dear Musters. Death was not unknown to our 70 some odd ship's complement—and I did indeed count that young boy's death as somehow the saddest, most poignant of all. And I certainly see that death's rude intrusion into your Journey has forged a further link between our experiences. I do agree with you that life is precious and not to be taken for granted!! Though I was fortunate to feel a completion to my life as Death neared, I must confess I am enjoying this opportunity to once again experience the exhilaration of contemplating the delights—and the Mysteries—of Life on Earth!

PPS: And please extend my Regards to Prof. Kohn. I look forward to hearing from him directly some day!

January 28, 2007

Dear Charles Darwin:

As always, great to hear from you!

Your comments on my earlier report of the cause of local extinctions in the Galapagos are fascinating. I was of course aware that you had difficulty in applying Lyell's explanation of extinction (as due pretty much always to physical environmental change) when it came to explaining the extinction of the mega-fauna of South America that occurred in the very recent geological past. I was also aware that you had briefly (1835-1837) toyed with the notion of racial senescence.

What was it like to find yourself inspired by—but at the same time often disagreeing with, Lyell? After all, virtually his entire second volume (which Prof. Kohn informs me you received just after your experiences unearthing the bones of those big fossils at Bahia Blanca in the Fall of 1832) is a diatribe against Lamarck and his evolutionary ideas. That second volume, in contrast to nos. 1 & 3, reads to me more like a lawyer's brief rather than a sober, dispassionate work of science—except in the few chapters where Lyell's discussions of what we now call "ecology" I find highly original and downright brilliant. Lyell, after all, was a barrister before he took up geology!). In the end, you wound up disputing Lyell not just over extinction, but over the whole enchilada—the "Mystery of Mysteries"—your adoption of transmutation. Evolution.

At the risk of sounding lugubrious, I suppose it is natural that, as our journey to the Galapagos nears its end, we find ourselves immersed in the twin subjects of death and extinction—the one of individuals, the other of Species. In the course of this trip, many of us have been rereading your Diary and, especially, your Journal of Researches (aka "Voyage of the Beagle")—especially, of course, the part devoted to your visit to the Galapagos.

I'll now take the liberty of quoting to you your final sentence of the Galapagos section as published in your first edition of 1839. It is your final reflection on the uncanny level of tameness of most Galapagos animal species—a tameness that for the most part is still very evident to us modern visitors. You wrote:

"We may infer from these facts, what havoc the introduction of any new beast of prey must cause in a country, before the instincts of the aborigines become adapted to the stranger's craft or power."

Beyond confirming that your ideas on extinction—as based primarily on biotic interactions—were already well in place by the end of the 1830s (and I agree you stuck by these ideas consistently throughout your subsequent work), this sentence proves incredibly prophetic in terms not only applicable to understanding the ecological havoc and extinction witnessed on the Galapagos since your visit—but (and you will find this no doubt unsettling) also to the ultimate explanation of the cause of extinction of the South American megafauna—the facts that in part brought you to embrace transmutation in the first place!!

First, the Galapagos: we humans were the biotic agent of the demise of those many populations of tortoises, iguanas, etc. etc. Here I must beg your pardon for yet another error in my previous blog: for not only did I (I admit) mistakenly say you were on James Island for 15 days (as you say, you were only there for 9 days), but I also accused you of contributing to the demise of the tortoise population there. I have since been informed by a member of our naturalist staff on board that there is still, in fact, a remnant population of tortoises on James; though greatly reduced in numbers, they are NOT extinct, as I erroneously reported—though sadly I was not wrong in announcing the demise of the James land iguana. I apologize for these errors.

But it is not just our direct predation on these native species that diminishes their numbers and drives some populations to extinction. For the goats and pigs we deliberately introduce to these islands are for our consumption; yes, the goats and pigs (and the dogs and cats who we bring for companionship, as well as the rats who always managed to tag along) are the proximal cause of the deaths/extinctions of iguanas, tortoises (and Hood mockingbirds, and so on)—but it is we who brought them—and thus we bear ultimate responsibility for the havoc, the death, the extinction, of the Galapagos "productions"—as you were wont to call them.

But here is the irony: you could not have known this, but that last sentence of your Galapagos discussion quoted above holds the kernel of explanation for what happened to those recently-extinct glyptodonts and other large native (edentate) mammals) whose bones you were so rightly excited over at Bahia Blanca in 1832. You did, most certainly, include humans in your transmutational views—as soon as you became convinced that life had evolved. We can see your inclusion of humans in your evolutionary views in your various Transmutation and Metaphysical notebooks of the late 1830s (though I remain suspicious that you were entertaining such notions even earlier—probably while still on the Beagle).

There was little known of the human fossil record before you died. You had speculated that we had our origin on the African continent—based on the existence of gorillas and chimpanzees still living there (though highly endangered—by ourselves, as we encroach on their forest habitats, turning them into farmlands; and even eat them!).

We now know so much more of our ancient evolutionary past. Fossils and molecular (genetic, i.e. the elements of heredity) evidence agree that our own particular species, Homo sapiens, arose in Africa sometime between 150,000-200,000 years ago. There had been earlier species in Africa, some of which occasionally spread into Europe and Asia.

Our own species began leaving Africa in migrational waves some 50,000 years or so ago. As we arrived in new places, our clever hunting skills, aided with spears and other instruments, took the local megafauna by surprise. I think of this spreading out of Africa as the first phase of the Sixth Extinction—the current world-wide disastrous loss of species that is strictly our doing: through destruction of habitats, over-exploitation of resources, pollution and the introduction of alien species.

Humans apparently reached the New World at least 20,000 years ago (some say even earlier), but did not get here in any great numbers until 12,000-13,000 years ago. As soon as we arrived, the great Ice Age fauna of mastodons, mammoths, wooly rhinos, giant bison and the like, immediately began to go extinct. There is little doubt that it was our hunting that finished these icons of the ice Age off forever.

Sir, there can be little doubt that it was predation by a newly-introduced species—OURSELVES—that killed off the glyptodont, the giant ground sloths etc etc. Your Galapagos quote shows that you had the key to the explanation in mind three years after you collected those fossils—but not knowing the details of human evolution and migration as we know them now, you have no basis for assuming that the forerunners of the Fuegians and other native peoples you met while in Patagonia were themselves relatively recent arrivals.

I wonder how different your intellectual journey culminating in your embrace of transmutation might have been had you had these few simple facts at your disposal?

Humans are the very best example of your principle that biotic causes—other species—can and do cause the extinction of other species. We are virtually the sole reason why we are losing an estimated 30,000+ species a year.

But having said that, I must tell you that in virtually all other instances—extinctions events in remoter periods of the geological past, at least for the past .5 billion years (i.e. since the advent of a multicellular life, leaving a reasonably good fossil record)—my colleagues and I tend to agree wholeheartedly with Lyell: extinction is invariably found to come in spasms, involving many species nearly simultaneously. And the cause is invariably found to be changes in physical environment, i.e. not biological in nature. Sometimes it is quick and catastrophic—as when extraterrestrial objects of great size collide with the earth. Other times (and far more commonly) the cause is more subtle and takes more time—as when global climate change modifies ecosystems too far too fast for many of the species of the existing fauna and flora to survive.

I cannot resist raising one further point: Our passengers on this cruise are an extraordinary bunch—well educated, and very tuned into the natural world. They have come to follow in your footsteps—and because the Galapagos, largely through your initial efforts, are so very famous.

One of these passengers has been reading your Descent of Man—in which you predict that "civilised" man will eventually cause the demise of inferior peoples. We overlook the characteristically Victorian nature of your prose here; you were not alone in assuming that industrialized nations bespoke an inherent superiority especially to the remaining hunter- gatherers of the world—such as the Fuegians you experienced both on shipboard and in their native land. (Indeed, you seem to say in your notes on the Fuegians that they, when exposed to English customs, readily learn the language and otherwise adopt the English way of life—implying to me at least that you saw a fundamental commonality of capacities to all of humanity).

But my fellow traveler's question was this: What would you now say about the supposed inherent superiority of civilized Man if you knew that our population has skyrocketed to over 6 billion; that we are (as alluded to above) the root cause of a devastation of life on earth of a magnitude not seen since asteroids (or comets) killed off the dinosaurs and so many other groups of animal and plant life, on both land and sea, some 65 million years ago? And what would you say to the fact that we have now devised means of eradicating, not only other species, but vast numbers of ourselves—through the harnessing of nuclear energy? For (you will hardly be surprised to learn) wars have not ceased to happen since your time. The threat of nuclear annihilation has been with us ever since I was born.

It is sadly true, as you anticipated, that we "civilized" people have driven many less powerful groups to oblivion. There are probably no bands of truly hunter-gathering peoples left at least unmodified by our arrival in their lands. Over 500 languages have been lost in the last century—as good a measure of any of the loss of cultural diversity on the planet. All due to the actions of the supposedly "superior" civilized Man.

What do you make of that?

As usual, a pleasure "talking" with you through the vehicle of this blog!

Yours,

Niles (Eldredge)

Previous Blog ::: Blog Index (main) ::: Next Blog