What a poor county in Texas might tell us about living longer

[This is an article I wrote for The Huffington Post for June 6, 2017.]

My wife has been going to the gym a lot lately, a gym with lots of older folk, people in their 70s and 80s. She says that, along with super-fit older women in her classes, there are some who are barely moving, carrying the tiniest weights and lifting them the tiniest amount, performing a kind of symbolic exercise. But they are obviously having a good time. They’re chatty in class, and chatty in the locker room. It’s social time at the fitness center in Reno.

Exercise is obviously helpful for living a long life, but I wonder if these women have hit upon something just as important. In his book The Blue Zones, about small regions where people often live past 100, Dan Buettner says that one of the common traits of people in these longevity hotspots—from Sardinia to Okinawa—is that they have strong and persistent social networks. They stay connected to family and friends even into extreme old age.

The gym in Reno might not be the greatest example of a social support group, but, quite possibly, it’s a lot better than nothing.

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I was thinking about those old women the other day, while poring over a map of the United States. This map, which has been all over the internet, comes from a study headed by a public health researcher named Laura Dwyer-Lindgren, and shows life expectancy by county for the whole country. Counties with long life expectancy are in blue, and the best of the best are in the deepest shade, so the longevity Blue Zones are easy to pick out.

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Life expectancy for the United States, by county, for those born in 2014 (both sexes combined). The lowest values are in dark red, the highest in dark blue. Map from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington.

I love a good map, and this one is a thing of informative beauty. It’s a window onto the character of the nation, onto racial inequalities and cultural diversity, onto immigration and assimilation, onto the vigor or decrepitude of regional economies, in short, onto endless social, political, and economic complexities. But some quick insight into the links between culture, wealth, and longevity can be had through a small part of this mapping project, namely, a list of the ten counties with highest life expectancy.

So here’s that Top Ten, a set of American Blue Zones:

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The top ten United States counties for life expectancy, from a study by Dwyer-Lindgren and colleagues. Income rank is the per capita rank among 3,143 counties from the American Community Survey, 2009-2013. Ethnic makeup is from the 2010 U.S. Census. The Aleutian Islands combine data for the Aleutians East Borough and the Aleutians West Census Area. The income rank for the Aleutians is the average for those two areas.

One thing that’s immediately apparent is that most of these counties are wealthy and white (meaning non-hispanic white). That’s not surprising; wealth usually means relatively good health care, and, more importantly, it probably often means being well-informed about healthy living habits, along with the means to easily make those habits a reality. To put it simply, wealth usually equals health, and most wealthy people in this country are white.

There’s a lot more to ponder here as well. Why all those Colorado counties? And why the remote Aleutian Islands? But what I want to focus on is the most obvious outlier on the list. That would be Presidio County, in West Texas, along the Mexican border. Presidio County is more than 80% Hispanic, and it’s not just poor, it’s really poor, ranking in the bottom 5% of all U.S. counties.

The flip side of “wealth equals health” is that poor Americans tend to be unhealthy and short-lived. So, one wonders, is there something peculiar about the way people live in Presidio County that opposes that tendency? It certainly doesn’t look like it: despite some Bohemian-style gentrification of Marfa, the county seat, Presidio County is pretty much as bad as you’d expect it to be when it comes to standard indicators of healthy lifestyles. For instance, people there are far more likely to be obese and far less likely to exercise regularly than the average American. And, too, measures of health care in Presidio County are toward the low end, as you’d expect for a poor county.

In other words, by its obvious measurables, Presidio County ought to be much closer to the bottom of the lifespan list than the top. Yet there it is at number 9, in the top third of the top 1 percent.

So what’s the story?

Well, the story at this point is incomplete, but it almost certainly has to do with something called “the Hispanic Paradox.” It turns out that, in the U.S., Hispanics as a group are poor, yet they’re relatively healthy and long-lived. In fact, for the country as a whole, the life expectancy for Hispanics is about 2.6 years longer than for non-hispanic whites.

Getting back to the map, notice that almost all of the counties along the Mexican border are in those good, blue shades, in spite of the fact that nearly all of them are poor. It’s a 2,000-mile-long incarnation of the Hispanic Paradox, stretching from the Pacific to the Gulf of Mexico. Presidio County does stand out as a Blue Zone even within that collection of border counties, but it no longer looks so extreme. It’s just a moderate outlier within a larger anomaly.

Researchers don’t all agree on what explains the Hispanic Paradox, but a likely key factor is what many of us would identify as the key to life in general: it’s about connections to other people. Hispanics tend to have strong ties to family and community, and are more religious than Americans as a whole; that’s probably intuitive to anyone familiar with Hispanic communities, but it’s also been confirmed by scientists who put numbers on such things. And there is now evidence from many studies that those sorts of ties—positive social networks, to put it a bit simplistically—translate to better mental and physical health.

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The idea that strong social ties can help explain Buettner’s Blue Zones and the Hispanic Paradox is food for thought. It brings to mind all our striving for some kind of recurring connection, from monthly book clubs to Sunday family dinners, from meditation groups to stitch ‘n bitch clubs to middle-aged men meeting up to play soccer or basketball. More specifically, the fact that, for most of us, those endeavors tend to be short-lived makes me wonder how a society might offer ways to sustain such connections in the face of a modern world that doesn’t value them enough.

These thoughts bring me back to the old women in the gym, the women who don’t exercise much, but chat a lot. The gym is part of a hospital, and it’s a place where the old, flabby, and weak don’t really stand out. You can go there and not feel self-conscious lifting very light weights, or displaying your startling lack of flexibility, or doing almost nothing at all. In short, it’s a comfort zone.

Is it possible to translate that comfort to other situations, to promote those social activities that tend to fall by the wayside? The message from Presidio County is that doing so might have a substantial influence on our health and longevity. And, in any case, whether those connections make us live longer or not, they’ll probably make us happier for whatever time we do have.

 

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The Soul on Your Plate

This is a review of “What a Fish Knows” by Jonathan Balcombe (Scientific American/FSG, 2016, 288 pp., $27). The review originally appeared in the Wall Street Journal, July 16-17, 2016.

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Some groupers hunt cooperatively with other species, including moray eels and octopuses, an example of the surprising complexity of fish behavior. Photo by Leonard Low from Australia (Flickr) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0%5D, via Wikimedia Commons

Last year the World Wildlife Fund ominously reported that ocean fish populations had dropped by 50% from 1970 to 2012, and those of some commercially important groups, such as tuna, had fallen further still. This huge decline in fish numbers was seen by many as an impending disaster—for the fishing industry, for people who depend on fish for much of their food, and, more generally, for the health of marine ecosystems that affect almost all life on the planet.

The WWF’s statistics entailed the demise of trillions of individual fish, but that fact was not really a topic of discussion. Hardly anyone seemed concerned about the deaths of the fish themselves.

That kind of reaction is typical. We treat fish, even more than other vertebrates, almost purely as resources to be exploited. We catch all sorts of fish for the sport of it; we keep them in aquaria as ornaments; and, of course, we support commercial fisheries that haul them in by the boatload, to be eaten by people, pigs, chicken and other fish (on fish farms) and to be used in making cosmetics, linoleum, insecticides and paint. We do all this with hardly a thought for the individual fish. We might show a small measure of concern by fishing with barbless hooks, or burying the pet goldfish in the backyard instead of flushing it down the toilet, but we are likely to follow such actions by grilling up some salmon fillets, happily anticipating the intake of healthy omega-3 fatty acids.

With “What a Fish Knows,” Jonathan Balcombe, who works at the Humane Society Institute for Science and Policy, wants to change this exploitative attitude. Mr. Balcombe believes that fish are sentient beings with rich inner lives. He wants people to care about fish as individuals, to think of them much as we would a pet cat or dog. He wants us to place fish in “our circle of moral concern.”

This might sound like a fool’s errand. To most people, it probably seems doubtful that a fish has any sort of inner life, much less a rich one. But Mr. Balcombe builds a persuasive argument. Writing in a straightforward, somewhat breezy style, he makes his case partly through a compendium of fascinating anecdotes and scientific findings that illustrate the complexity and creativity of fish behavior. Dozens of startling revelations emerge, including playful marine fish riding bubbles to the top of an aquarium, elephantfish “singing” courtship duets using electric pulses, and parasite-picking cleaner fish engaging in convoluted “economic” interactions with their “clients.” The cleaner-client relationship, in particular, involves remarkable subtleties, such as client fish punishing cleaners who do shoddy work and cleaners treating first-time clients with special care, like a shopkeeper cultivating the business of a new customer.

An especially eye-opening discovery places certain fishes in exclusive company, behaviorally speaking. Some groupers hunt cooperatively with other fish (and, bizarrely, even with octopuses), dividing up tasks based on their different abilities, which is perhaps itself an indication of intelligence. Beyond this, however, at least two kinds of groupers recruit hunting partners by aiming their heads down in the direction of hidden prey—in other words, groupers communicate by pointing. Outside of humans, pointing has been verified only in great apes and ravens, which, Mr. Balcombe notes, are “known to be Einsteins of the animal world.”

Collectively these various descriptions give a strong sense that at least certain fishes act much more like birds and mammals than most of us appreciate. For some people, that might be reason enough to treat fish ethically. But Mr. Balcombe hinges his argument for fish welfare on a further assertion that is more difficult to prove—specifically, that fish are sentient in the sense of feeling pleasure and pain. If this is true, then hurting a fish is akin to hurting a person and is wrong for the same reason.

To back up this claim, Mr. Balcombe points to observations of fish acting in ways that suggest joy or suffering. For instance, on the pleasure side, many fish seek out physical strokes from other fish or even from humans, a choice that has no obvious utilitarian purpose. On the pain side, a key study showed that trout injected with vinegar become oblivious to objects they would normally avoid, which Mr. Balcombe interprets as the fish being distracted by pain.

A skeptic might say that such findings do not prove sentience; a fish might act as if it can feel pleasure or pain without having the corresponding conscious experience. Maybe fish are like sophisticated robots, capable of amazing feats and apparent emotion but without any real feeling. (The same, of course, might be said of dogs, monkeys or even of other people, for none of us can truly experience what another being feels.)

Mr. Balcombe perhaps places too much emphasis on the controversial issue of feeling pleasure and pain. One wonders if inclusion in “our circle of moral concern” has to be based on that ability. Might it be enough that a creature displays intricate, problem-solving behavior, as some fishes do? Can we at least put fish in an intermediate category reserved for beings that show obvious signs of complex cognition, and some indications of feeling pain and pleasure, even if these qualities seem less likely in them than in, say, a parrot or a dog? And have we avoided pondering the inner lives and welfare of fish in part because of our long, exploitative relationship with them?

Mr. Balcombe does not explicitly address these questions, but the fact that a reader might ask them and truly wonder about the answers indicates that his book has done its job. In the epilogue, Mr. Balcombe sets up a final, hopeful plea for the better treatment of fish by quoting Martin Luther King Jr.: “The arc of the moral universe is long, but it bends toward justice.” It is a mark of the book’s effect that these words, which might initially have seemed presumptuous or even silly when applied to fish, come across as natural and relevant.

—Mr. de Queiroz is the author of “The Monkey’s Voyage: How Improbable Journeys Shaped the History of Life.”

Are Migrating Cancer Cells Like Rafting Monkeys?

Early in the morning, before getting sucked into the e-world, sometimes even before having coffee, I’ve been reading a book called Cancer: The Evolutionary Legacy by a British medical researcher named Mel Greaves. This probably sounds like an astoundingly bad way to start the day, but Greaves’ tone is pretty light, and he doesn’t get into the individual stories of cancer sufferers. It’s a concept book, and an incredibly fascinating one. I’m only making it through a few pages a day, because I’m constantly stopping to digest some point, and turning the margins into snarls of exclamation points, arrows, and scribbled thoughts.

Greaves obviously loves a good analogy, and when he describes metastasis—the establishment of cancer cells in new locations within the body—what comes out, strangely enough, is pure biogeography, and, in particular, long-distance colonization. The malignant cells in their original location (colon, breast, or wherever) are hemmed in by physical boundaries and barriers, like “an overpopulating and localized species of animal” confined to an island, with the surrounding sea cutting off escape. When a few cells manage to break out into the bloodstream or lymphatic circulation, “it is rather like a desperate migrant crossing the China Sea in a fragile vessel.” Most of these cells will not survive the journey, but “given the number that try and the time available, inevitably a few may succeed.”

In other words, the movement of cancer cells is a lot like monkeys crossing the Atlantic or other instances of chance, overseas dispersal, even extending to the idea that a small probability of success for any single attempt can translate to a much higher one given enough time. That quote about “the number that try and the time available” could have come from the paleontologist George Gaylord Simpson writing about overwater dispersal by Cenozoic mammals. Or, for that matter, from Darwin arguing for the natural colonization of oceanic islands.

Digital Capture

Figure drawing: Edward Burne-Jones. Map: Ktrinko—own work, CC0, https://commons.wikimedia.org/w/index.php?curid=17169364

The analogy doesn’t stop there, though; in fact, the detailed parallels pile up almost to the point of absurdity. Thus, once a cancer clone makes it to a new location, it is more likely to thrive “in a similar environment or ecosystem to that from which it came—one part of the bladder to the other, skin to skin.” So the successfully colonizing cancer cell is like, say, a shrub from a tropical rainforest that, after dispersing, gains a foothold because it happens to find itself in another tropical rainforest.

Continuing on, some types of cancer cells are better migrants than others, just as ducks and rats are more likely overseas colonists than salamanders and kangaroos. Numbers at the source location are important in both instances—of cancer cells in the one case and of individual organisms in the other. Access to thoroughfares can be critical—cancer cells multiplying next to a large blood vessel are like monkeys living by a river that might wash them down to the sea. And lymph nodes can act as way stations for migrating cancer cells, the equivalent of stepping-stone islands for migrating species.

Greaves’ analogy makes it clear that metastasis is, at its core, a random process, but with the probabilities heavily influenced by various factors. The randomness of it—chance cell movement, like chance dispersal—gives some insight into the fact that two people could develop the same kind of cancer simultaneously, yet, in one, the disease might spread almost immediately whereas, in the other, it might take years to metastasize. Meanwhile, the influencing factors, such as access to many blood vessels and lymph nodes, make sense of why some kinds of cancer often persist for years without spreading, while others can be expected to metastasize very quickly.

Following up on these thoughts, I did a quick search in the Web of Science for mathematical models of  metastasis. None of the studies mentioned overseas dispersal or rafts of vegetation, but they did give me some reason to tweak the biogeographic analogy to more closely match the disease situation. It appears that, for at least some kinds of cancer, the initial and subsequent tumors might interact with each other beyond the original one-way colonizations. In particular, the tumors within a person seem to receive new “seeds”—colonizing cancer cells—from one another, and the re-seeding influences their growth. This makes me think that monkeys rafting across the Atlantic, which happened only once as far as anyone knows, is not the best analogy for these cases. The migrating cancer cells are more like Darwin’s finches colonizing and re-colonizing islands in the Galápagos.

Darwin’s evolutionary ideas have been fruitfully translated to all sorts of areas outside of their original domain, including such things as constructing genealogical trees of languages, describing the fates of memes, and creating computer algorithms that solve problems by mimicking natural selection. Close to the topic at hand, many people have recognized that the growth and spread of cancer within the body is a Darwinian process—selection occurring at the level of competition among cells—and that this knowledge might prove useful in developing new treatments.

To end on a vaguely practical note, I wonder if models of chance dispersal—the mathematical embodiment of ideas set forth by Darwin, Simpson, and others—might be applied to the process of metastasis. Could these biogeographic models give us some novel insight into that process, either by introducing new variables or a different kind of analysis? Could they provide something more medically useful than a metaphor?

Another Monkey’s Voyage: Panamacebus and the Central American Seaway

monkey in ceramic sm

One of the great stories in biogeography is that, when the Isthmus of Panama emerged about 3 million years ago, a flood of species passed over this new corridor between the New World continents, some going north, others south. If you’ve seen opossums, armadillos, or porcupines in North America, jaguars (or, more likely, jaguar tracks), maned wolves, tapirs, or llamas in South America, you’ve encountered the descendants of animals that crossed over the isthmus. This narrative is so well known that it has both a name and an acronym that many biologists (and even others) instantly recognize; it’s called “The Great American Biotic Interchange,” GABI for short.

The 3-million-year age of the land bridge is widely accepted, so much so that many studies have used it to stamp a date on the evolutionary separation of marine “sister species” living in the Pacific and the Caribbean. (According to the simple version of the story, those species split from each other because of the rise of the isthmus.) But in the last few years, some geologists and biologists have questioned that age, and have claimed that the isthmus arose much earlier, at least 6 million years ago and perhaps as early as 23 million years ago. Those radical new claims have been attacked, maybe “slammed” would be a better word, but these earlier ages for the land bridge have found their way into scientific articles and popular news accounts.

With that background in mind, I read a paper that just came out in the journal Nature, “First North American fossil monkey and early Miocene tropical biotic interchange” by Jonathan Bloch and others. Based on seven fossil teeth, Bloch et al. describe an extinct monkey species from 21-million-year-old ash fall deposits that were exposed by dynamiting as part of an expansion of the Panama Canal. The location of this Miocene fossil, called Panamacebus, means that monkeys must have made it from South to North America millions of years earlier than anyone had thought.

So what are the implications of this new fossil discovery for putting an age on the formation of the Isthmus of Panama and the story of the Great American Biotic Interchange?

An immediate thought is that land mammals are not good at crossing sea barriers—Darwin said that in The Origin of Species—so the ancestors of Panamacebus probably moved by land to North America. The new fossil, therefore, is another argument for the early emergence of the isthmus.

I don’t think that’s the conclusion to be taken from this study though (and it isn’t a conclusion made by the study’s authors). For one thing, various kinds of evidence—biological, geological, and oceanographic—indicate the 3-million-year age is correct. Also, it’s not at all far-fetched to believe that monkeys could have rafted across the narrow Central American Seaway thought to have separated North and South America 21 million years ago. As I pointed out in The Monkey’s Voyage, there are many well-established cases of overwater dispersal by primates, including at least two—monkeys dispersing from Africa to South America over the Atlantic, and the ancestors of lemurs colonizing Madagascar from Africa—that involved much longer journeys than a crossing of the Miocene Central American Seaway. And, in fact, the monkeys that made the trans-Atlantic voyage were the ancestors of Panamacebus, while other South American monkeys probably rafted to Caribbean islands. In other words, even within this one branch of the primate evolutionary tree, there have been long overwater colonizations.

The story of the isthmus is, of course, partly about the major pulse of animals that moved over the new land bridge. But it’s also about a surprising number of groups that dispersed between the continents before the bridge emerged, including not only monkeys, but northward-moving sloths, frogs, flightless terror birds, and a capybara relative, and southward-moving snakes, toads, raccoon relatives, and rodents. Most surprising of all, a couple of groups of freshwater fishes somehow made the journey north across the seaway, perhaps using a plume of fresh water spreading from the mouth of a major river. (The dispersal of those fishes does give me a little pause about the age of the isthmus, much more so than the monkeys.)

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Xenodon merremi, part of a group of some 300 species of South American snakes derived from a species that dispersed over water from North America. (Photo by Mateus S. Figueiredo—Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=42796144)

A final twist to the story is that the living monkeys in Central America are not the descendants of the ones that crossed the seaway. The monkeys that rafted north likely did not give rise to any modern species and, as near as I can figure from a quick look at evolutionary trees, the ancestors of all these living monkeys probably reached Central America after the Isthmus of Panama emerged. As much as I have argued for the importance of overseas dispersal, I have to think the most likely scenario for the squirrel, spider, howler, white-faced, and owl monkeys that now live in Panama and points north is that they used the land bridge, ambling or swinging their way to North America.

 

Back-side Scuttlers

The other day, I saw a Williamson’s Sapsucker on the trunk of a pine and tried to get a picture, but the bird kept scuttling around to the other side of the tree, obviously avoiding me. I would move, he would move, I would move, he would move, etc. Sometimes I could just see his head peeking out from behind the trunk, apparently waiting to see what I’d do next. I never did get a clear shot of him and had to settle for this photo of sapsucker “wells” in the tree.

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Sapsucker wells without the sapsucker

The scuttling sapsucker reminded me of other woodpeckers I’ve seen doing exactly the same thing, but also of a beetle (Saxinis sp.) I found on a hike last year in the Carson Range, just outside of Reno. This beetle was clinging to a flower stalk of a buckwheat, and, like the sapsucker, it scuttled to the back side, which seemed kind of silly because the beetle was wider than the stalk. It was like the kid playing hide-and-seek who crouches behind a rock too small to conceal him. And the beetle reminded me of anole lizards on tall rainforest trees on islands in the Panama Canal, and also of mantis insects in some woods I can no longer place (Louisiana?)—the anoles and mantises were back-side scuttlers too.

 

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Saxinis beetle on buckwheat (Eriogonum)

Which makes me wonder—how many other species do this? I would guess that, if you’re a highly visual creature and you spend a lot of time moving around on natural cylinders you can easily hide behind (trunks or branches or stalks, depending on your size), then scuttling to the back side is probably a standard part of your repertoire. If that’s true, there must be thousands of different kinds of back-side scuttlers out there. And, now that I’m thinking about this, and have written it down (there’s a lot to be said for the act of writing it down), I’ll be on the lookout for the next one.

After a while, I circled the pine more quickly, trying to catch up with the sapsucker. But he was gone, having scuttled and then, while out of my view, taken flight. Beetles and mantises can pull that move too. Anoles can’t fly but they still have an out—they just go scurrying up the tree.

 

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Savannah Anole (Anolis roquet)—not the species I saw in Panama, but probably also a backside scuttler. By 0x0x10C (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0), via Wikimedia Commons

 

The House Crow’s Voyages: Oceanic Dispersal in the Age of Humans

My father-in-law spends a lot of time sailing—he’s made two solo trips across the Atlantic, among other things—and he says that land birds often hitch rides on his boat. One time, for instance, a small songbird sailed with him across the Adriatic, from Italy to Albania, and a Great Blue Heron rode with him for five hours on a trip from Cape Cod to Maine. (He even has a video of the heron, looking as uncomfortable as you’d expect a heron on a sailboat to look.)

Although I’m a birder, I had no idea that birds catching rides on boats was such a common thing. But apparently it is, and there’s even a semi-official term for the phenomenon: it’s called “ship-assisted dispersal.” For example, many songbirds from the Americas that show up in the Azores probably made some part of the voyage on cargo ships. And Great-tailed Grackles, New World birds that are not considered good overwater dispersers, have appeared in Hawaii and Spain, almost certainly having ridden rather than flown to those places, thousands of miles from their normal range.

These birds that hitch rides to distant lands are exciting for birders, but generally aren’t very significant in the long run; that is, they do not establish new populations “by ship.” They arrive, hang around for a while, and, almost always, die without ever reproducing.

Unless they’re House Crows.

The history of the House Crow (Corvus splendens) has become so entwined with humanity’s that I’ve begun thinking of it as the poster bird for the Age of Humans. It’s apparently the only wild bird species that not only does well around people, but actually can’t live without us; populations of these birds are only ever found around human settlements. (Even “trashy” city birds like the House Sparrow and Rock Pigeon can’t make that claim.) The native range of the House Crow is mostly within the Indian subcontinent, and it’s thought (or, at least, it’s reported on Wikipedia) that the human population explosion there produced an explosion of House Crows also. (On the other hand, should we drive ourselves to extinction, the House Crow will probably flame out with us.)

It turns out that House Crows have a special thing not just for our settlements (and our garbage), but also for ships. In particular, they often alight on ocean-going vessels, where they presumably live off the crew’s scraps, and can then be carried hundreds or even thousands of miles to distant ports. And, unlike most other birds that hitch rides on ships, House Crows often survive and thrive in their new outposts. Maybe that’s because several crows arrive at once from the same ship, or because port towns tend to be great habitats for these birds, or simply because there are so many of these crow voyages taking place—I don’t think anybody really knows the answer.

In any case, House Crows are now established in cities and towns all around the Arabian Peninsula and down the east coast of Africa. Some of these populations came from purposeful introductions, but most of them seem to be the result of birds catching rides on their own across parts of the Indian Ocean. They’re sort of the stowaway rats of the bird world, except that they ride in plain sight.

Distribution of the House Crow around the Indian Ocean. The introduced populations are thought to be mostly from ship-assisted dispersal, either from the native range or from earlier introduced populations. The map is redrawn from a worldwide map of the House Crow's distribution by Colin Ryall (http://www.housecrow.com/?page_id=28). Used with permission.

Distribution of the House Crow around the Indian Ocean. The introduced populations are thought to be mostly from ship-assisted dispersal, either directly from the native range or from earlier introduced populations. The map is redrawn from a worldwide map of the House Crow’s distribution by Colin Ryall (http://www.housecrow.com/?page_id=28). Used with permission.

Tangentially, the relationship between House Crows and people on boats has worked the other way around too, with sailors making use of the birds’ navigation skills. Specifically, ancient Indian and Singhalese (Sri Lankan) mariners apparently took House Crows along on their boats, and, if the mariners needed to find land, they would release a crow and follow its course, like Noah with the dove that led him to Mt. Ararat. (The Vikings used other kinds of crows in the same way, and these stories make me wonder whether Noah’s dove, if it has any connection to reality, was actually a crow.)

The long-distance colonizations of House Crows all seem to have taken place within the last 130 years or so, probably reflecting the invention of faster ships and the growth of shipping traffic, and, barring some concerted international effort against these birds, their ship-assisted expansion will no doubt continue. Anticipating this, a group of scientists recently made an ecological niche model which suggests that House Crows might thrive in significant parts of all continents except Antarctica. And, in fact, lone crows already have made it to ports on all of those continents, and small populations have become established in the Netherlands and in Florida (beginning in the 1990s and 2000s, respectively). The incredible spread of this species naturally reminds me of Lyanda Lynn Haupt’s book “Crow Planet.” Haupt was referring especially to the success of the American Crow, but maybe one day we’ll be talking, with more literal truth, about a “House Crow Planet.”

On one level, the history of the House Crow is discouragingly familiar, yet another illustration of the runaway train that is the Age of Humans, an age in which the Earth’s biota is increasingly and inexorably tied to what we are doing.

Less depressingly, though, I think of its story as an example of a wild bird species sort of turning the tables on us, using its very crow-ish adaptability to take advantage of our technological ingenuity, hopscotching from ship to port to ship. I don’t relish the idea of House Crows spreading around the world, but there’s something impressive about the fact that they might, without us even wanting them to.

For more information on the distribution, dispersal, and general biology of House Crows, see Colin Ryall’s House Crow Monitor website.

New study on early monkeys in the Americas

Since the centerpiece story in my book is the case of monkeys apparently crossing the Atlantic Ocean from Africa to South America, I now have a special (and vested) interest in studies about this example. So, when I heard about a new paper called Eocene primates of South America and the African origins of New World monkeys,” I quickly devoured it, even skimming the supplementary material.

The paper, by Bond et al. in the journal Nature, reports fossil teeth of monkeys from Amazonian Peru, from what the authors believe to be Late Eocene deposits. Three findings from this study seem especially important: (1) If the estimated age of the specimens is correct, they greatly extend the fossil record of monkeys in the New World, from about 26 million years ago (the age of the previous oldest known New World monkey) to some 36 million years ago. (The older age, by the way, is still fully consistent with molecular clock estimates for the separation of New World and Old World monkeys.) (2) The teeth represent three different species, indicating a surprising diversity of early South American monkeys. (3) The new species, Perupithecus ucayaliensis, described from the best-preserved tooth, shows an apparent evolutionary connection to a specific extinct African monkey, Talahpithecus.

That last result is particularly relevant for validating the African origin of New World monkeys (although previous evidence from fossils also pointed to that scenario). However, the grouping of the South American Perupithecus with the African Talahpithecus, rather than with all other New World monkeys, also implies a more complex ocean-crossing scenario than previously imagined. Specifically, that relationship requires either two separate crossings from Africa to South America or a single such dispersal followed by another from South America back to Africa (see figure).

Two scenarios for the dispersal of monkeys to/from the New World. Left: two Africa to South America colonizations. Right: Africa to South America colonization followed by "back-dispersal" to Africa. The evolutionary tree is from the Bond et al. paper.

Two scenarios for the dispersal of monkeys to/from the New World. Left: two Africa to South America colonizations. Right: Africa to South America colonization followed by “back-dispersal” to Africa. Perupithecus is the newly described extinct species. The evolutionary tree is from the Bond et al. paper.

These more complex dispersal scenarios can’t be discounted; if monkeys crossed the Atlantic once, I suppose they could have done it twice (although a scenario involving a “back-dispersal” to Africa has, as far as I know, never been supported for a land vertebrate). But, if I had to bet on it, I would choose a different explanation: the grouping of Perupithecus with Talahpithecus is wrong. That wouldn’t be a shock considering that Perupithecus is known from just a single tooth and Talahpithecus from three teeth, two of them broken. Also, in the analysis by Bond et al., the pairing of these two taxa is very tenuous. (A tree that does not group these two taxa is just one step longer than the most parsimonious tree.) I wouldn’t be surprised if it turns out that Perupithecus groups with other New World monkeys, with Talahpithecus outside of this group. That result would bring us back to the simpler scenario of a single crossing of the Atlantic.

In any case, Bond et al.’s study is a big step forward in deciphering the history of monkeys in the New World. I’m hoping that they or others will eventually find other critical fossils that will further flesh out the story of how and when monkeys reached the Americas. Maybe it’s too much to ask, but it would be fantastic to have a skull and some other bones from these early New World monkeys!

Thanks to Darren Lettinga for letting me know about this paper.

Central American squirrel monkey (Saimiri oerstedii). Photo by Manuel Antonio from Wikimedia Commons.

Central American squirrel monkey (Saimiri oerstedii). Photo by Manuel Antonio from Wikimedia Commons.