Years ago, I realize that most of Darwin’s arguments, in On the Origin of Species, are underlain by evidence Darwin would have observed prior to setting foot on the Galapagos Islands. This includes fossil evidence from mainland South America, bio-geography in that region and on the Falklands, other observations, and material in the literature, some of which he was carrying with him.

It is not that the Galapagos didn’t matter. They mattered a great deal, as a natural laboratory of evolution. And it is not clear to what degree Darwin had realized his own theory before, during, and after his Galapagos visit. But, reading whichever version of The Voyage of the Beagle you like, that Darwin’s post hoc reconstruction of the ontogeny of his own reasoning starts out long before the Beagle closed in on Valparaiso, on the Pacific Coast.

Origins of Darwin’s Evolution: Solving the Species Puzzle Through Time and Place is a refreshing look at Darwin’s voyage incorporating this perspective.

From the Publisher:

In On the Origin of Species (1859), Charles Darwin presented his evidence for evolution and natural selection as its mechanism. He drew upon his earliest data gathered during his voyage on the HMS Beagle, which included collecting mammalian fossils in South America clearly related to living forms, tracing the geographical distributions of living species across South America, and sampling the peculiar fauna of the geologically young Galápagos Archipelago that showed evident affinities to South American forms. By the end of the voyage, he came to the realization that instead of various centers of creation, species evolved in different regions throughout the world. However, except for some personal ponderings, he did not express this revelation explicitly in his notebooks until shortly after his return. Over the years, he collected more evidence supporting evolution, but his early work remained paramount: it became the first paragraph of On the Origin of Species and encompassed three separate chapters, as well as later appearing in his autobiography.

Many discussions of Darwin’s landmark book give scant attention to this wealth of evidence and today we still do not fully appreciate its significance in Darwin’s thinking. In Origins of Darwin’s Evolution, J. David Archibald explores this lapse. He also shows that Darwin’s other early passion, geology, proved a more elusive corroboration of evolution. On the Origin of Species dedicated only one chapter to the rock and fossil record, as it appeared too incomplete for Darwin’s evidentiary standards. Carefully retracing Darwin’s gathering of evidence and the evolution of his thinking, Origins of Darwin’s Evolution achieves a new understanding of how Darwin crafted his transformative theory.

This is a well written, relatively short, monograph that that emphasizes the role of Historical Biogeography in Darwin’s thinking, by an experienced and well informed American paleontologist, who also wrote Extinction and Radiation: How the Fall of Dinosaurs Led to the Rise of Mammals and Dinosaur Extinction and the End of an Era.

The Triassic is old. This book is new. That is a hard to beat combination.

Let’s see … The Triassic is about here:

(You can also look it up in this PDF file supplied by the USGS.

It is situated between two major extinction events, and is especially interesting because it is during this period that modern day ecological systems and major animal groups took a recognizable form. The preceding Permian, if contrasted with modern day, would form a very stark contrast while the Triassic would be at least somewhat more recognizable.

But of course the Triassic was in many ways distinct, different, and fascinating. Dinosaurs arose during the Triassic. The Triassic is also famous for its enormously large insects. It was also the time of Pangaea, where most of the Earth’s land was concentrated instead of being more or less spread out as it is now. Mammals, or at least the progenitors of what we now know of as mammals, arose then as well.

The Triassic was hot compared to today, and dry. Lots of sandy, arid-land deposits visible today date from this period. The poles were temperate, and the middle regions of the one giant continent was probably … very continental (mainly, dry).

So, all this adds up to the simple fact that the Triassic was a very interesting time period, and I assume that you would like to know a lot more about it. That would be where the new book, Triassic Life on Land: The Great Transition, comes in. This new volume in a series on “Critical Moments and Perspectives in Earth History and Paleobiology” (of which there are several other interesting must-have installments) comes in.

Sues and Fraser’s accessibly priced volume is neither a popularization of palaeontology nor a monotonous monograph of esoterica. It is a scholarly but readable detailed yet succinct description of this incredibly interesting time period. This is the kind of book that you will sit down to relax with, but do so with a pack of post-it notes handy just in case you need to mark something. Triassic Life .. is sufficiently detailed and well documented (excellent references and index) to be used as a textbook in a middle level palaeontology course, and sufficiently engaging for you to use as a source book for your next cocktail party.

The authors are widely recognized and respected experts in their field. The publisher did an excellent job with the book, which is very heavily illustrated and well laid out. Yet, most of the illustration are very nicely done line drawings and black and white photos, which keeps the price of this volume down despite the nice paper and excellent binding.

The book has eleven chapters, seven of which serve as mini-monographs of specific Triassic sub periods in specific geographical locations (such as “Late Middle and Late Triassic of Gondwana” and “Late Triassic of the Western United States”). Each of these chapters gives the basic information on where, when, and what for that particular subset of paleontological phenomena. Chapter 9, “Two Extraordinary Windows into Triassic Life” focus on two cases of Konzentrat-Lagerstätten (places of especially good preservation or richness): Solite Quarry in the eastern US and Madygen in Central Asia. Triassic insects. Very nice.

Chapter 10 is an overview of the large scale pattern of biological change during the period, and Chapter 11 examines the Triassic end-times, exploring the possibility of an end-Triassic impact, and other issues.

If you have an evolution-oriented relative or friend who’s birthday is coming up, now’s your chance: The book is new enough and specialized enough that there is no way they’d have it already. And, it looks enough like a coffee table book that others looking on will see it as a great gift even if it is a bit over the top in geek points.

The likelihood that your yard slopes one way or the other … statistically … depends in large part on what region you live in. (Here I’ll be speaking mainly of the US, but the principle applies broadly.) If you live in New England, your yard is more likely to slope up. If you live in the Midwest/Plains, your yard is more likely to slope down

This is because in New England, we humans build our settlements around rocks. Because there are rocks. (If you don’t believe me, note that all the famous rock farms are in New England.) You get a big aircraft carrier size rock, you build your streets around its base, the houses face the streets, and the yards travel up the rock in the back.

In the glaciated Upper Midwest, we build our settlements around swamps and ponds, again, because there are a lot of them. They don’t call Minnesota the “Land of Lakes” for its rocks! In fact, rocks are so hard to find around here that when people do find them, they put them out in their front yards like sculptures.

So, you build your road on the high ground, put the houses along the road, and by definition (high vs. low) the yards slope down to the swamp. Which, of course, you fill in with dirt, but it’s still low ground.

This is why dogs in New England are less hyper than dogs in the midwest. When all the yards slope down, even tall fences do not cover the view from the back windows to all the neighbor’s yards, and thus, all the neighbor’s squirrels and all the neighbor’s dogs. But in New England, what with the rocks and all, the view from a person’s yard may consist mainly of the person’s yard and not so much the neighbor’s yards. So, in the Midwest, a dog may have an acre or more of wooded parkland squirrel habitat to look at, while in New England, maybe one squirrel, maybe none. (And, removing the squirrels in New England has a better chance of working long term as well.)

Obviously, this will vary a lot. What I’ve just said applies more to suburbs than to urbs (though not entirely). In South Minneapolis, for instance, the swamps are all parks. Really. Go look at any park in South Minneapolis and you’ll see that it’s a major low spot. If it is big enough, there will be a lake down there, if not, just a filled in swamp. The local geology dictates that the yards are mostly flat (and that, therefore, the airport is nearby!) and that the main thing you see in your yard is your garage and the alley. So, South Minneapolis yards are more like New England yards than one might expect. And, in New England, if your yard backs on a stream, obviously, you have a low area, but you don’t get the above described view, because the stream will be accompanied by an edaphic woodland riverine forest. People who live in those houses have very nervous dogs, because … of the raccoons.

This relationship between landscape and lifestyle is fairly trivial, but there are a thousand (well, OK, dozens) of ways in which regional geology and physical geography shape your life, and they can add up. These aspects of the land add to cultural feature of a region to form a palpable gestalt.

Look around you. How is your cultural landscape shaped by bedrock, sediments, drainage patterns, and patterns of natural vegetation?

And it’s pink.

In 1984, Hickmann and Lipps said the following about the various pieces of evidence giving age estimates for the Galapagos islands:

… all are less than about 2 million years old. This age, together with independently determined geologic ages, indicate that the islands emerged from the sea relatively recently and that all evolution of the islands’ unique terrestrial biota occurred within the past 3 to 4 million years.

Subsequently, it was realized that the present day islands are not the whole story. It is not the case that the evolutionary divergences among species we see on these islands had to happen in the few million years that the present day Islands seem to have been in existence. The Galapagos island chain includes a number of sea mounts which were islands in the past that have disappeared beneath the sea. The geology is somewhat more complex here than in other similar island chains, but the principles are the same.

There is an oceanic plate moving south east across a hot spot. The hot spot produces volcanoes. As the plate moves past the hot spot, volcanism ceases locally and the island formed by the volcano stops growing. (If the hot spot is still hot, a new volcano, ‘upstream,’ will start to form.) Then, the top of the island, now volcanically dormant, begins to erode down and the base and core of the volcano shrinks. These forces convert the volcano into a smaller and smaller island, until finally it submerges beneath the sea and becomes a sea mount.

There are probably sea mounts in the Galapagos dating back to about eight million years, maybe over ten million, but the extant islands seem to be only a few million years old. Any understanding of the biogeography of the animals on the Galapagos has to be understood in this dynamic geological context.

Now that we have that context worked out, enter the Pink Iguana. The Pink Iguana is both a species of Galapagos land iguana and a kind of martini. The Galapagos lizard version was discovered only recently, around the time that scientists were saying that all the evolution that happened in the Galapagos had to occur over a few million years time. Even more recently, a group of scientists have done a study of the genetic relationships between the Pink Iguana and the other land iguana’s on the Galapagos, and have come to a few remarkable conclusions. But first, let us address the remarkable confusions we face in looking at Rosada.

B and C are the rosada variety, the others are standard yellow models.

There is not clear taxonomy of the Galapagos land iguanas. They are all of the genus Conolophus. Several years ago, Snell, Snell and Tracy described the status of the land iguana’s and indicate that at the time there were thought to be perhaps five or six populations known historically, at least two of which were extinct, and perhaps one relict as a very small group of remnants. The remaining iguanas were thought to be divided into three populations, two of which have at some time or another been considered to be distinct species. These species were called Conolophus pallidus and Conolophus subcrislalus. Typically, one sees the Galapagos land iguana referred to simply as Conolophus subcrislalus. The pink iguana, believed to be a new species, seems to be unnamed.

From the new study by Gentile and others, just out in PNAS:

The most surprising result was the deep divergence of the rosada lineage at the basis of the Conolophus clade. This species alters the current thinking about the timing of diversification of land iguanas, which was previously supposed to have occurred in the Pleistocene Epoch …. our estimate sets the origin of this relict lineage back to a period when at least some of the present-day islands had not yet formed. In fact, the oldest extant islands in the archipelago, San Cristo´bal and EspanË?ola, are at least 2.35 and 3.3 million years old, respectively, … given its present distribution, the rosada form clearly represents a conundrum because it occurs only on Volcan Wolf, which is considered younger than Volcan Sierra Negra (0.53 million years…) …

So, the pink iguana, which is probably a new species first noted by park employees about twenty years ago, may represent the primordial land iguana of this island chain, and thus may represent the form that split with the marine iguana quite a bit earlier in time. Even so, the timing of diversification of the Galapagos land iguanas is recent in relation to the island chain itself, and because of the marine-terrestrial split, we know (or at least have strong confidence) that the land iguanas have been here for a very very long time.

What does all this mean? No one knows, but here is what I think:

The Galapagos are way over eight to ten million years old, and some time back around then were in habited by iguanas from somewhere. Now keep in mind that the landscape looked pretty different back then. North and South America were not joined by the Panama land bridge, and there was probably a lot of movement of fauna and flora between what is now the eastern equatorial Pacific and the Caribbean.

Land iguanas have always moved from island to island on a very low level in the Galapagos. Islands have slowly formed, grown large, then shrank, and slipped beneath the sea over time. But the temporal scale of island formation and disappearance is probably much slower than the temporal scale of iguana movement between islands. Furthermore, it is possible that inter-island movement becomes more likely when the islands become smaller, for ecological reasons.

In the end, I’m not surprised by what the authors of this recent paper are surprised by. I would expect only a vague correspondence between island history and animal movement. The question that I would like to see addressed is this: Why are the basal iguanas rare and the derived iguanas more common?

G. Gentile, A. Fabiani, C. Marquez, H. L. Snell, H. M. Snell, W. Tapia, V. Sbordoni (2009). An overlooked pink species of land iguana in the Galapagos Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0806339106

Snell, H.L., Snell, H.M., Tracy, C.R. (1984). Variation among populations of Galapagos land iguanas (Conolophus): contrasts of phylogeny and ecology Biological Journal of the Linnean Sociey, 185-207

C. S. HICKMAN, J. H. LIPPS (1985). Geologic Youth of Galapagos Islands Confirmed by Marine Stratigraphy and Paleontology Science, 227 (4694), 1578-1580 DOI: 10.1126/science.227.4694.1578

This is also discussed here, at Not Exactly Rocket Science.

… We hypothesize that these individuals are myxoedematous endemic (ME) cretins, part of an inland population of (mostly unaffected) Homo sapiens. ME cretins are born without a functioning thyroid; their congenital hypothyroidism leads to severe dwarfism and reduced brain size, but less severe mental retardation and motor disability than neurological endemic cretins. We show that the fossils display many signs of congenital hypothyroidism, including enlarged pituitary fossa, and that distinctive primitive features of LB1 such as the double rooted lower premolar and the primitive wrist morphology are consistent with the hypothesis. We find that the null hypothesis (that LB1 is not a cretin) is rejected by the pituitary fossa size of LB1, and by multivariate analyses of cranial measures. We show that critical environmental factors were potentially present on Flores, how remains of cretins but not of unaffected individuals could be preserved in caves, and that extant oral traditions may provide a record of cretinism.

There are a handful of reasons to criticize these results based on the results themselves, but there is also a broader overarching reason to coming to the point that pathology explains this fossil population only as a last resort.The authors claim that Myxoedematous endemic cretinism occurs in various places at rates approaching 5%, but his is an overstatement in two ways. First, enlarged goiter and a range of iodine deficiency outcomes occur in some populations in Central Africa and Indonesia, but full blown ME dwartism of the type they attribute to Flores is very very rare in these areas. In fact, there are only two descriptions of this conditions used in this study, attesting to the rarity of this condition.Many of the osteological traits the authors use are also primitive traits. Primitive traits can show up in descendant populations either because of early branching (phylogenetically) or genetic changes, and are thus not good sources for phylogeny. Placing the Flores Hobbits within rather than along side a human lineage is a phylogenetic conclusion. This is a problem that will be difficult to avoid in this sort of analysis.The authors use local stories of cretin-like people to bolster their case. These stories may or may not have relevance, but in many places in the world there are stories of not-exactly-human forms that live out in the wild. Leprechauns come to mind, but there are many other examples as well. The assertion that this is evidence in support of a particular form of pathology is very weak.There is a broader reason to distrust pathological explanations. This is using the assumption, as suggested in the paper (especially in regards to local mythology) that the cretinoids lived on their own in the forest, even if they were part of a larger population.What if I told you about a major corporation that was run entirely by people with Down Syndrome, severe Autism, with a board of directors entirely comprised of advanced Alzheimer patients. This corporation produced products that were packed on trucks at a loading dock staffed only by comatose or quadruplegic workers. Further, I told you that this company was quite successful.You would not believe me.People with various (aforementioned) disabilities can certainly live productive lives, and can be integrated into any broader system and do fine, but this requires integration and compensation. We would not assume that an accounting firm staffed entirely by people incapable of doing math or a special forces army unit staffed entirely by people with no leg or arms would function. Why, then, do we assume that a subsociety, living on their own in the forest, made up of people with severe mental and physical deficiencies would survive?To assume that this is possible is to seriously underestimate the required capacities for humans to live as foragers. This is a commonly made, Western-biased, post-Agricultural centered, and racist mistake. The deeper assumption plays from the hero-myth of human history and evolution. “Advanced” societies, such as those with agriculture, pastoralism, cities, complex kinship systems, space ships, widget factories, etc. are assumed to be made up of people who are intrinsically (genertically and/or culturally) advanced over their hunter-gatherer forbearer’s.Nothing could be farther from the truth. Where data are available, we tend to find that hunter-gatherer populations have measurably larger brains, notably smaller percentages of mentally disabled participants, and on direct ethnographic observations, are extra smart.It is possible that this condition of cretinism was endemic to some population living in this area, and the cretins were sent off the forest, perhaps fed and cared for minimally, and did not actually function as an independent foraging society. I might believe that. But such a subset living on their own with sufficient persistence to leave numerous fossils and a reasonably rich archaeological record is extraordinarily unlikely.The authors do address this idea to some extent.

ME endemic cretins escape the severe neurological deficits of neurological endemic cretins … having milder mental deficiency, greater self-reliance and a general lack of mobility deficits (Wang et al. 1982). In agricultural populations, ME cretins are well cared for, but in seasonally mobile hunter-gatherer populations, the limited mobility of cretins could lead to separation, particularly of adult cretins. Use of caves by adult cretins and lack of burial would explain the cretin remains at LB, while seasonal mobility, alternative shelters and systematic burial would explain the absence of the remains of normal individuals. A population (n=25-100) with 1% cretinism is calculated to produce 4-15 deaths of adult cretins per kiloyear, which is enough to explain the discovered remains at LB.

By the way, where Cretinism occurs in Central Africa, it occurs only among agricultural populations who have moved into the region where iodine is rare within several centuries time, and not among indigenous foragers.

This paper is discussed by Afarensis, HERE.Obendorf, P.J., Oxnard, C.E., Kefford, B.J. (2008). Are the small human-like fossils found on Flores human endemic cretins?. Proceedings of the Royal Society B: Biological Sciences, -1(-1), -1–1. DOI: 10.1098/rspb.2007.1488

Tigers don’t carry passports or follow immigration policies, but a new plan will allow the big cats to roam freely across landscapes in Asia, without breaking any laws. The Wildlife Conservation Society (WCS) and the Panthera Foundation will establish a 5,000-mile-long “genetic corridor” for tigers from Bhutan to Burma. The term refers to a swath of interconnected lands where wildlife populations can travel with less risk of inbreeding.First announced at the United Nations on January 30, the proposed corridor would span eight countries and represent the largest block of tiger habitat left on Earth. It would wind through much of Bhutan, northeast India, Myanmar, Thailand, and Malaysia, and potentially connect to Laos, Cambodia, and Vietnam. The new king of Bhutan, his Majesty Jigme Khesar Namgyel Wangchuck, has already endorsed the corridor and requested other heads of state to support similar efforts.At the recent UN meeting, Dr. Alan Rabinowitz, director of Science and Exploration Programs at WCS and the co-director of Tigers Forever–a WCS/Panthera Foundation collaboration–made a clear request for additional approval and assistance from other leaders.”While Asia’s economic tigers are on the rise, wild tigers in Asia are in decline,” he said. “Much like the call-out for global agreements on banning tiger parts in trade, a similar cross-border initiative for genetic corridors is key to the survival of the tiger. Tiger range states need to work together, as tigers do not observe political borders nor do they require a visa or passport to travel where habitat and prey remain.”Rabinowitz specified that corridors did not have to be pristine parkland but could include agricultural areas, ranches, and other multi-use landscapes–just as long as tigers could use them to travel between wilderness areas….

More at the Wildlife Conservation Society

Hearing … of the remains of one of the old giants, which a man told me he had seen on the banks of the Parana, I procured a canoe, and proceeded to the place. Two groups of immense bones projected in bold relief from the perpendicular cliff [but] I could only bring away small fragments of one of the great molar-teeth … sufficient to show that the remains belonged to a species of Mastodon. The men who took me in the canoe, said they had long known of them, and had often wondered how they had got there: the necessity of a theory being felt, they came to the conclusion, that … the mastodon formerly was a burrowing animal!

In remote St. Fe …

A tooth which I discovered … interested me much, for I at once perceived that it had belonged to a horse. Feeling much surprise at this, I carefully examined its geological position, and was compelled to come to the conclusion, that a horse, which cannot … be distinguished from the existing species, lived as a contemporary with the various great monsters that formerly inhabited South America. Mr. Owen and myself, at the College of Surgeons, compared this tooth with a fragment of another, probably belonging to the Toxodon, which was embedded at the distance only of a few yards in the same earthy mass. No sensible difference in their state of decay could be perceived; they were both tender, and partially stained red. … Certainly it is a marvellous event in the history of animals, that a native kind should have disappeared to be succeeded in after ages by the countless herds introduced with the Spanish colonist! But our surprise should be modified when it is already known, that the remains of the Mastodon angustidens (the tooth formerly alluded to as embedded near that of the horse, probably belonged to this species) have been found both in South America, and in the southern parts of Europe.

Weighty considerations of the distribution of extinct and extant fauna lead Darwin to the neighborhood of modern geological concepts.

Very few species of living quadrupeds, which are altogether terrestrial in their habits, are common to the two continents, and these few are chiefly confined to the extreme frozen regions of the north. The separation, therefore, of the Asiatic and American zoological provinces appears formerly to have been less perfect than at present. The remains of the elephant and of the ox have been found on the banks of the Anadir (long. 175° E.), on the extreme part of Siberia, nearest the American coast: and the former remains, according to Chamisso, are common in the peninsula of Kamtschatka. On the opposite shores, likewise, of the narrow strait which divides these two great continents, we know, from the discoveries of Kotzebue and Beechey, that the remains of both animals occur abundantly: and as Dr. Buckland has shown they are associated with the bones of the horse, the teeth of which animal in Europe, according to Cuvier, accompany by thousands the remains of the pachydermata of the later periods. With these facts, we may safely look at this quarter, as the line of communication (now interrupted by the steady progress of geological change) by which the elephant, the ox, and the horse, entered America, and peopled its wide extent.

Now, here we have Darwin on the verge of understanding the rise of the Panama Land bridge (or something like that) based on the biogeography. The above passage, the following passage, and other material is very frustrating. If Darwin was not such a geological gradualist he could have advanced geology to the 1950s with a single fell swoop of reasoning!!!!

The occurrence of the fossil horse and of Mastodon angustidens in South America, is a much more remarkable circumstance than that of the animals mentioned above in the northern half of the continent; for if we divide America, not by the Isthmus of Panama, but by the southern part of Mexico, .. where the great table-land presents an obstacle to the migration of species, … we shall then have two zoological provinces strongly contrasted with each other. Some few species alone have passed the barrier, and may be considered as wanderers, such as the puma, opossum, kinkajou, and peccari. The mammalogy of South America is characterized by possessing several species of the genera of llama, …, tapir, peccari, opossum, anteater, sloth, and armadillo. If North America had possessed species of these genera proper to it, the distinction of the two provinces could not have been drawn; but the presence of a few wanderers scarcely affects the case. North America, on the other hand, is characterized by its numerous rodents, and by four genera of solid horned ruminants, of which section the southern half does not possess a single species.

Just so you know, South and North America were separated, and had largely independent mammalian evolution (and migration), until very recently, about five million years ago, when the isthmus of Panama was raised.Darwin is seeing the very time-deep echo of this event, masked by subsequent migration of North American mammals in to South America, and clouded by the more pressing (to him) question of Old World and New World relationships.It is interesting that the monkey’s (appearing in both the old world and new world tropics) don’t freak him out. They freak me out.

The other posts in this series can be found by clicking this link.

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I will now give an account of … the Struthio Rhea, or South American ostrich. This bird is well known to abound over the plains of Northern Patagonia, and the united provinces of La Plata. It has not crossed the Cordillera; but I have seen it within the first range of mountains on the Uspallata plain…. The ordinary habits of the ostrich are familiar to every one. They feed on vegetable matter; such as roots and grass; but at Bahia Blanca, I have repeatedly seen three or four come down at low water to the extensive mud-banks which are then dry, for the sake, as the Gauchos say, of catching small fish. Although the ostrich in its habits is so shy, wary, and solitary, and although so fleet in its pace, it falls a prey, without much difficulty, to the Indian or Gaucho armed with the bolas. When several horsemen appear in a semicircle, it becomes confounded, and does not know which way to escape. They generally prefer running against the wind; yet at the first start they expand their wings, and like a vessel make all sail. On one fine hot day I saw several ostriches enter a bed of tall rushes, where they squatted concealed, till quite closely approached. It is not generally known that ostriches readily take to the water. Mr. King informs me that at the Bay of San Blas, and at Port Valdes in Patagonia, he saw these birds swimming several times from island to island. …When swimming, very little of their bodies appear above water, and their necks are extended a little forward: their progress is slow. On two occasions, I saw some ostriches swimming across the Santa

The following passage is thought by some Darwin scholars to reflect one of Darwin’s most significant “aha” moments, leading to his understanding of evolutionary processes. The bird described here is known as the Avestruz Petise, and was named by the ornithologist Gould as Rhea darwinii. However,since the bird was earlier named (based on reports, not specimens) Pterocnemia pennata (the Lesser rhea), Darwin’s name does not survive today in the annals of taxonomy.Read the passage then I’ll note its presumed significance.

…I repeatedly heard the Gauchos talking of a very rare bird which they called Avestruz Petise. They described it as being less than the common ostrich (which is there abundant), but with a very close general resemblance. … The few inhabitants who had seen both kinds, affirmed they could distinguish them apart from a long distance. … This species occurs most rarely on the plains bordering the Rio Negro; but about a degree and a half further south they are tolerably abundant. …They are said to prefer the plains near the sea. When at Port Desire, in Patagonia (lat. 48°), Mr. Martens shot an ostrich; and I looked at it, forgetting at the moment, in the most unaccountable manner, the whole subject of the Petises, and thought it was a two-third grown one of the common sort. The bird was cooked and eaten before my memory returned. Fortunately the head, neck, legs, wings, many of the larger feathers, and a large part of the skin, had been preserved. From these a very nearly perfect specimen has been put together, and is now exhibited in the museum of the Zoological Society. Mr. Gould, who in describing this new species did me the honour of calling it after my name, states, that besides the smaller size and different colour of the plumage, the beak is of considerably less proportional dimensions than in the common Rhea …

Eventually, Darwin made note of the fact that over time, distinct but similar species seemed to differ by grades (such as in size) in the fossil record, as and the same pattern could be seen across geographical space. In his notebooks, he was to eventually note that the variation across space and time seemed to be two ways of looking at the same pattern of change. He made the link between biographical variation in the Rhea and the finches on the Galapagos and similar variation seen in the fossil fauna such along the South American Atlantic coast.In a note book dated to “1836 and after” (late in the voyage), Darwin wrote a passage that has been the focus of a great deal of attention. In it, he demonstrates his waffling about the nature of species. He frames his introspection in terms of “creation” and at the same time struggles with the evidence from biogeography, which suggests that closely related species would have a common ancestor. He also addresses extinction. Darwin is essentially asking “… where are the transitional forms?”Remember, this is his notebook writing … it is very much stream of consciousness, conflicting, and hard to understand. I’ll provide you with the entire relevant passage unedited except for the removal of some geologizing. It is painful and wonderful at the same time:

Speculate on neutral ground for 2 Ostriches: bigger one encroaches on smaller;–change not progressive; produced at one blow, if one species altered. …Should urge that extinct Llama owed its death not to change of circumstances; reversed argument, knowing it to be a desert. Tempted to believe animals created for definite time:–not extinguished by change of circumstances.The same kind of relation that common ostrich bears to Petisse–[S. Darwinii] and difft. kinds of extinct Guanaco to recent. In former case position, in latter time (or changes consequent on lapse), being the relation, as in first cases distinct species inosculate [To pass into; to join or unite so as to become continuous; to blend] so must we believe ancient ones [did] not gradual change or degeneration from circumstances, if one species does change into another it must be per saltum–or species may perish. This representation of species important, each its own limit and represented. Chiloe creeper; Fournarius, Callandria. Inosculation alone shows not gradation.an animal in two (gemmiparous by nature or by accident) we see an individual divided either at one moment or through lapse of ages. Therefore we are not so much surprised at seeing Zoophite producing distinct animals, still partly united, & egg which becomes quite separate. Considering all individuals of all species as each one individual divided by different methods, associated life only adds one other method where the division is not perfect.Dogs, Cats, Horses, Cattle, Goat, Asses, have all run wild and bred, no doubt with perfect success. Showing how creation does not bear upon solely adaptation of animals. Extinction in same manner may not depend. There is no more wonder in extinction of species than of individual.When we see Avestruz [the Petisse or smaller Ostrich, Struthio Darwinii] two species certainly different, not insensible change; yet one is urged to look to common parent? Why should two of the most closely allied species occur in same country? In botany instances diametrically opposite have been instanced–

Of this passage, Nora Barlow (in her publication on these notebooks) wrote, in 1945:

We can see the mill at work, grinding out hypotheses. … In biological fields the throes of question and doubt, of comparison of masses of facts, of discardings and reviewing, were still to continue for 23 years before the Theory of Evolution as we know it, found expression.

Well said, Nora.

LADEN, G., WRANGHAM, R. (2005). The rise of the hominids as an adaptive shift in fallback foods: Plant underground storage organs (USOs) and australopith origins. Journal of Human Evolution, 49(4), 482-498. DOI: 10.1016/j.jhevol.2005.05.007

THE Beagle arrived on the 24th of August, and a week afterwards sailed for the Plata. With Captain Fitzroy’s consent I was left behind, to travel by land to Buenos Ayres.

I tried Googling that … using “get directions.” Google maps was unable to compute a route. In fact, Google Maps has no roads whatsoever in Argentina. But, I was able to make a map showing the two locations, to give you an idea of what this must have been like. Darwin walked (well, there were horses) between these two points:And along the way, he found some fossils. Here are brief excerpts describing some of his finds. As you read through this (it’s long, but I’ve tried to edit it down as much as possible) keep in mind the following things: Evidence for evolution, climate change, large scale global synthesis, connections between observations and theory. It is all here. This is Darwin coming to an understanding of the Big Picture of Evolution.

At Punta Alta, a low cliff, about twenty feet high, exposes a mass of [sediment] containing numerous recent shells. We may believe a similar accumulation would now take place … where tides and waves were opposed. In the gravel a considerable number of bones were embedded. … the following list may give some idea of their nature: 1st, a tolerably perfect head of a megatherium, and a fragment and teeth of two others; 2d, an animal of the order Edentata, as large as a pony, and with great scratching claws; 3d and 4th, two great Edentata related to the megatherium, and both fully as large as an ox or horse; 5th, another equally large animal, closely allied or perhaps identical with the Toxodon …, which had very flat grinding teeth, somewhat resembling those of a rodent; 6th, a large piece of the tesselated covering like that of the armadillo, but of gigantic size; 7th, a tusk which in its prismatic form, and in the disposition of the enamel, closely resembles that of the African boar; it is probable that it belonged to the same animal with the singular flat grinders. Lastly, a tooth in the same state of decay with the others: … but the part that is perfect, resembles in every respect the tooth of the common horse.* … the space in which they were collected could not have exceeded one hundred and fifty yards square. It is a remarkable circumstance that so many different species should be found together; and it proves how numerous in kind the ancient inhabitants of this country must have been…. in another cliff of red earth, I found several fragments of bones. Among them were the teeth of a rodent, much narrower, but even larger than those of the Hydrochærus capybara; the animal which has been mentioned as exceeding in dimensions every existing member of its order. There was also part of the head of a Ctenomys; the species being different from the Tucutuco, but with a close general resemblance.The remains … were associated … with shells of existing species. … similar to the species now living in the same bay: it is also very remarkable, that not only the species, but the proportional numbers of each kind, are nearly the same [as the modern fauna] … If I had not collected living specimens from the same bay, some of the fossils would have been thought extinct … We may feel certain that the bones have not been washed out of an older formation, and embedded in a more recent one, because the remains of one of the Edentata were lying in their proper relative position (and partly so in a second case) ……From the shells being littoral species … we may feel absolutely certain that the remains were embedded in a shallow sea, not far from the coast. From the position of the skeleton being undisturbed, and likewise from the fact that full-grown serpulæ were attached to some of the bones, we know that the mass could not have been accumulated on the beach itself. …From the general structure of the coast of this part of South America, we are compelled to believe, that the changes of [elevation] have … of late … been in one direction, and … very gradual. If, then, we look back to the period when these quadrupeds lived, the land probably stood at a level, less elevated only by a few fathoms than at present. Therefore, its general configuration since that epoch cannot have been greatly modified; …The surrounding country, as may have been gathered from this journal, is of a very desert character. … Here, then, is an apparent difficulty: we have the strongest evidence that there has occurred no great physical change to modify the features of the country, yet in former days, numerous large animals were supported on the plains now covered by a thin and scanty vegetation.That large animals require a luxuriant vegetation, has been a general assumption, which has passed from one work to another. I do not hesitate, however, to say that it is completely false; and that it has vitiated the reasoning of geologists, on some points of great interest in the ancient history of the world. The prejudice has probably been derived from India, and the Indian islands, where troops of elephants, noble forests, and impenetrable jungles, are associated together in every account. If, on the other hand, we refer to any work of travels through the southern parts of Africa, we shall find allusions in almost every page either to the desert character of the country, or to the numbers of large animals inhabiting it. The same thing is rendered evident by the many sketches which have been published of various parts of the interior. When the Beagle was at Cape Town, I rode a few leagues into the country, which at least was sufficient to render that which I had read more fully intelligible.

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