Renaissance Circles: Ginkgoes and Fruit-Eating Crocs

A long while back, I accepted the idea that the classic “Renaissance Man” archetype is impossible. It wasn’t really possible during the period when the term was coined, but Thomas Jefferson and Georges Cuvier and Richard Owen could fake it. Even through the Eighteenth Century, an individual with a reasonable accumulation of knowledge on most subjects? Sure, if you were limited to concentrating on works in your native tongue and a smattering of references in three or four other languages. Today, there’s simply no way to be that much of a generalist. Any of the pure or applied sciences alone sees so much advancement in a year that standard print books on physics or palaeontology are hopelessly outdated by the time they see print six months after the author typed “-30-“, and now further education depends more on unlearning inaccurate or obsolete information picked up during earlier bouts of academia.

This isn’t to say that learning is worthless, or that there’s no point in trying to keep up. Instead, what I’m seeing, thanks to the wonders of the Intertubes, is the evolution of what I like to call “Renaissance circles”. These are groups of people specializing in widely diverse fields, who themselves have friends with enough knowledge in those fields that they can make connections and build relationships impossible within those specialties. Thirty years ago, the cross-pollination between, say, astronomers and palaeontologists that ultimately allowed the the acceptance of an extraterrestrial impact as the cause of the famed Cretaceous-Paleogene extinction was an anomaly. These days, that sort of mass mind isn’t just common, but in fact inevitable.

Case in point. A few months back, I was lucky enough to catch a lecture tied to the book Ginkgo: The Tree that Time Forgot by Peter Crane, with Dr. Crane discussing his longtime love with Ginkgo biloba and its extinct cousins. While the ginkgos used to range every continent during the days of Pangaea, they gradually died back through the Mesozoic Era and the earlier parts of the Cenozoic, with the last holdouts in the northwest of North America and the eastern portion of Asia until about 8 million years ago. Right about then, ginkgoes disappear from the fossil record, and they were understandably thought to be extinct by researchers in the West until the first samples of wood and leaf arrived in Europe from China. One species, Ginkgo biloba, survived that final cull, and survived through China and Japan for thousands of years thanks to human intervention. Today, ginkgoes are found on every continent but Antarctica, but like the resurgence of the Wollemi pine, it’s due to people enjoying the beauty of the tree and encouraging its growth. Between the symmetry of the fan-like leaves in spring and summer, and the stunning canary yellow foliage in autumn, it’s hard not to fall in love with ginkgoes except for one little issue.

The issue, sad to say, is the ginkgo’s fruit. Ginkgo produce separate male and female trees, and the vast majority of ginkgo grown in urban areas are male. (The photos above are of ginkgoes on the grounds of the Fort Worth Botanic Garden, and they’re all male.) That’s because the females produce clusters of squishy fruits a little larger than a cherry, with apricot-colored flesh surrounding a stout seed with a strong shell, roughly the size of a pistachio. With the exception of the nut itself, very popular when roasted, that’s the last analogy to anything edible that you’ll hear about ginkgo fruit. My ex referred to the stench of ripe ginkgo fruit as “cat shit on a stick”, and I experienced this firsthand when I lived in Portland, Oregon in the late 1990s. A Lutheran church in downtown, about a block from my mail drop, had planted male and female ginkgoes between the church itself and the city sidewalks with no concern for the aftermath, and walking those sidewalks in October was a nightmare. The ripe fruit splattered onto the sidewalks when ripe, rapidly turning into an orange mush in the gutters with a stench that would have burned out the nose hairs of a dead nun. Worse, the strength and shape of the nuts meant that they didn’t break easily underfoot, and a badly placed heel meant that you went sliding into that gutter. The only good news was that ginkgo stench wore off after about an hour, and didn’t stain clothing, so it wasn’t quite as bad as rolling around in a litter box, but only just.

Now here’s where it gets interesting. Firstly, nothing disturbed that fruit while it was relatively fresh. I didn’t test this personally, but unlike durian, nobody is ever going to sell ginkgo smoothies as the latest fad taste sensation, unless coprophilia suddenly becomes VERY popular. The nuts would eventually be snagged by local crows, but I never saw bird nor mammal rushing to grab them up if given a choice between them and acorns. Likewise, considering that the conditions in the Pacific Northwest were extremely conducive to growing ginkgo in the wild, you’d think that the forests outside of Portland and Seattle would be overtaken with ginkgo trees, but they really only showed up in areas where they’d obviously been planted by humans. Since humans weren’t around when ginkgo last lived in the Portland area, I wondered what factors caused their seed dispersal and germination.

Here’s where it gets even more interesting. Ginkgo nuts will germinate on their own, but apparently the natural germination rate within the nut shells is very low. Almost every bonsai book I’ve encountered that discusses ginkgo as a good bonsai tree recommends gently cracking the shell with pliers and removing the embryo inside, instead of merely planting the nut and waiting for it to germinate on its own. This suggested that the nut needed some kind of chemical or mechanical treatment to weaken the shell. But what? Whatever it was, it was in short supply in Portland, otherwise the city would have been overrun with ginkgo a century ago.

And now it gets bizarre. Late last week, Dr. Thomas Holtz, a man whom I want to be like when I finally grow up, shared a very fascinating article on frugivorous habits of modern crocodylians. While modern crocodiles, alligators, and caimans give every indication of being obligate carnivores, they apparently have a fruit-eating streak that runs across the entire group. (I haven’t found anything on gharials eating fruit, but that may just because nobody has chronicled it yet.) The article went even further, suspecting that crocodylians might be involved with seed dispersal in the wild by spreading them in their feces. Problem is, alligators and crocodiles tend to be rather secretive about their constitutional habits, so everything is conjecture at this time.

DING! The light went off in my head: “what if the previous success of ginkgoes was due to their nuts being spread by dinosaurs, crocodylians, and other archosaurs in their dung?” The idea of large animals carrying, processing, and dispersing seeds of large trees isn’t anything new: just talk to anyone familiar with the Osage orange (Maclura pomifera) and its probable spread across North America in the guts of Columbian mammoths, mastodons, and ground sloths during the Pleistocene. I brought this up with Dr. Holtz, and he informed me that, at least as far back as his grad student days, alligators were notorious for scarfing up dropped ginkgo fruit.

Now, here’s where surmisal turns into testable hypothesis. The surmisal is that ginkgo fruit may have developed its particular rank odor to attract now-extinct crocodyloforms and other archosaurs and descendants, including dinosaurs and large birds, and encourage them to swallow the seeds. Said seeds were big enough to act as gizzard stones in the species with gizzards, with the seeds passing through the gut after having most of the shell coat worn away by mechanical action in the gizzard. Much like many seeds, from eucalypts to Capsicum peppers, those seeds would be deposited in new locales with a healthy dollop of fertilizer around them, giving them a decided advantage in germination and growth over other species that didn’t utilize the powers of crocodile crap. Considering the number of crocodylian species that thrived through most of North America until the end of the Miocene, when Earth started its current cooling cycle, it’s possible that one or more species surviving until about 8 million years ago was a major vector for ginkgo nuts, and the ginkgo died out in North America and most of Asia shortly after. (And now I want to go digging for more information on the distribution during the Pliocene and Pleistocene on the range of the Chinese alligator [Alligator sinensis].) Now all that’s left is finding evidence to back up this surmisal.

The potential evidence comes in three forms. The toughest would be to examine gizzard stone collections still preserved within the ribcages of fossil crocodylians: this is tough partly because so few were preserved and because ginkgo nuts may or may not preserve under those conditions. The second would be to look for ginkgo nuts within crocodylian coprolites, and that requires finding incontrovertible crocodile coprolites from the right place and the right age. Finally, there’s real-time experimentation: offering ripe ginkgo fruit to alligators, confirming that they ate the fruit of their own volition, and then following them around with a baggie for a few days until I got the seeds back. And considering that I have a good friend who (a) forgets more about crocodylians every night when he goes to sleep than I’ll ever learn, (b) has access to captive alligators and crocodiles, and (c) is up for all sorts of odd experiments, I now have about 11 months to plan this out and get a good supply of ripe ginkgo fruit. Don’t wait up.