A couple of weeks ago we heard, among others, a West Virginia group called the Dry Branch Fire Squad at Hardly Strictly Bluegrass. One of the musicians told a string of jokes that I think I would have found less amusing if they had been about Arkansas. “They just found our great aunt,” he said. “Her name was Ardi … That’s the best picture she ever took. They say she could climb trees and walk upright. I never saw her do neither.”
Another fossil find got considerably less media attention than the early hominid Ardipithecus, but is significant on its own terms, and will require some revision to accepted ideas about biogeography—the science that explains why organisms are found where they are. Earlier this year, Michael Engel, an entomologist at the University of Kansas, and two colleagues reported in the proceedings of the California Academy of Sciences the recent discovery of a honey bee in Nevada.
The honey bee we all know (Apis mellifera) is, of course, native to Europe. It became naturalized in North America early enough that some scholars thought it had originated here. In “Notes on the State of Virginia,” Thomas Jefferson wrote that the local Indians called it “the white man’s fly,” indicating that once the bees showed up, European settlers were not far behind.
All the living honey bee species are confined to Europe and Asia. North America has the primitively social bumblebees and a host of solitary types, but no highly social (eusocial is the term) bees like A. mellifera.
But that wasn’t always the case. Engel, et al., found their bee, which they named Apis nearctica, in a fourteen-million-year-old shale formation in the Stewart Valley Basin in west-central Nevada. The remains were partially disarticulated, but enough components were there that it could be diagnosed as a honey bee. A. nearctica closely resembles a contemporary species from Germany, Apis armbrusteri. It was found in company with fossil ants and wasps, one group of which is characteristic of forested environments.
Since only one specimen was found, we can’t know whether A. nearctica was social or solitary. But its European relative A. armbrusteri was represented by a swarm of workers that had succumbed to carbon dioxide at a hot spring. (Ludwig Armbruster, an arch-category splitter, described a number of separate species based on variations among the bees and named them after his friends and colleagues. Later researchers decided they were all the same kind of bee.)
Two questions come to mind: how did A. nearctica get to Nevada, and what happened to it? Through geological time, North America has had land connections with both Asia and Europe. During the Miocene epoch, when A. nearctica was extant, only the route from Asia—an early version of Beringia—was open.
There was a lot of traffic between North America and Asia at the time. Mastodons, rhinos, pronghorns, true cats, bears, beavers, and pit vipers were moving into North America from Asia, while horses and camels headed the other way. Honey bees appear to have evolved in Europe or Asia, with at least one representative reaching North America.
The bee or its ancestors would have encountered temperate forests along the way, but would eventually have run up against an arid region stretching from central Mexico up through the Midwest. That would have blocked its access to a potentially suitable habitat in the south, which may never have been colonized by honey bees.
The Miocene has been described as a golden era of North American biodiversity, with a large-mammal fauna rivaling that of modern Africa. But the climate became cooler and drier toward the end of the period, which ended with several waves of extinctions. The authors suggest that A. nearctica may have been unable to adapt to these less congenial conditions. Maybe—a wild guess—its demise may have had something to do with the replacement of perennial herbs by annuals during the late Miocene.
If honey bees had persisted in the Americas, who knows what ramifications would have ensued. Would the Iroquois have invented frosted cornflakes?
The story of the Nevada honey bee illustrates once again that absence of evidence is not evidence of absence. It also underscores how much the fauna of North America, micro- as well as mega-, has changed over time, and how problematic the categories of native and alien can be. After all, the West’s feral horses could also be seen as returning natives, and there are those who would like to stock the Southwest with lions, camels, and elephants. (Let’s not even get started on the wild turkeys.)