The story of mysterious life-forms that existed nearly 600 million years ago might involve rocks in, of all places, Hingham. A radical idea, to be sure. Then again, the provocative scientist leading a study there is anything but conventional.
(Photo by Fred Collins)
Geologist and paleontologist Mark McMenamin slouches his 6-foot-4 frame over the sandstone slab hes holding. He tilts it to the light coming through a window of a lab at Mount Holyoke College, and the elliptical impressions on the charcoal-colored stone come into view. They look like thumb marks in fresh concrete. This could be any old rock, from anyplace. But this rock happens to be from a cove in suburban Hingham, and if McMenamin is right, those small dimpled rings are fossils of the oldest structurally complex life-forms on earth.
Whether theres evidence in Bostons backyard of a group of soft-bodied organisms about 575 million years old called the Ediacara biota is a question that McMenamin might eventually be able to answer. This month and next, he will lead a study at a site on the Weymouth Back River with a grant from the Keck Geology Consortium. Although McMenamin, 49, isnt the first to examine the area, which he and others believe contains the oldest fossils in the Northeast, no modern peer-reviewed study of it has been published. And his work there is likely to raise the profile of the local geology. Theres a story here that is longing to be told, McMenamin says of the site, if we just read the rocks properly. The story, however, is complicated, not only because of the mysterious nature of these organisms but also because of the maverick nature of the scientist himself.
Researchers largely believe the frond- and disk-shaped Ediacara (pronounced ee-dee-ACK-er-uh) biota to be a multicellular blip in lifes development. Ediacarans emerged after the first advanced cells and then mostly disappeared just before the burst of life in the fossil record known as the Cambrian explosion. Because many Ediacarans bear little resemblance to other fossils or living creatures, they were once thought to have been a separate kingdom, neither plant nor animal, and scientists say some of them might still represent a failed experiment in life. More recently it has been hypothesized that some of them lie on the evolutionary tree as we know it, more or less related to sponges, corals, or worms. But its still an open question. Either way, they are what came before what came before us, seven times older than T. rex.
Ediacaran fossils, which range in size from less than an inch to more than 3 feet, have been found in about 30 locations around the world, including Australia, Russia, Namibia, and North Carolina. The idea that they might be here makes sense, given that part of Eastern Massachusetts is geologically similar to a rock terrane in England and Newfoundland, where these fossils have also been found. But opinions are mixed on whether the rings on the South Shore rocks merit further examination. They were described in a 1923 paper and thought then to be inorganic. But McMenamin thinks they are fossils of Aspidella, a type of Ediacaran. So does Ed Landing, a paleontologist who has done unpublished work on the rings at the New York State Museum, where some are on display. But Sam Bowring, an MIT geologist, says the rings may not be biological and are just a local curiosity. I dont think there are any unique attributes, he states.
McMenamin, a native of Oregon who has been at Mount Holyoke since 1984, doesnt hesitate to challenge conventional thought. He made headlines in 1995 when he declared he had discovered, in Mexico, what were the oldest examples of Ediacarans. He also has said Ediacarans showed signs of developing heads and nervous systems, concluding the development of humanlike intelligence elsewhere in the universe is nearly inevitable.
McMenamin, easygoing and quick to laugh (his voice-mail greeting promises to get back to you before the passage of a significant amount of geologic time), says constant questioning is a key to his work. But just as he draws praise for stirring discussion and helping explain early life to the public, he is also described as self-promoting and has frustrated colleagues by proposing hypotheses that, they say, rely more on philosophy than on science. While commending McMenamins ability to find fossils in the field, James Gehling, a paleontologist at the South Australian Museum who worked with McMenamin in Namibia, called McMenamins 1998 book The Garden of Ediacara an embarrassing piece of New Age nonsense.
I would like to see Mark come back to doing what he can do, and that is to do the hard and tedious work of searching old rock surfaces, says Gehling in an e-mail.
McMenamin is about to do just that in Hingham, but his project is viewed as an encroachment by Northeastern geologist Richard Bailey, who began researching the rings there in 1990. It was Baileys British colleague Benjamin Bland who revitalized local interest in the rock impressions by reading the 1923 paper, concluding they were fossils, and being the first to locate the specimens in place rather than in unattached fragments. You dont transgress on someone elses work, Bailey says. Other scientists say Bailey, who has written about the rings with Bland in field guidebooks, should have published his research in peer-reviewed journals by now. Bailey, who believes the fossils bear only a superficial resemblance to Aspidella, plans to publish in a year or two and attributes the delay to the complexity of the rocks.
McMenamin says his project will help move the science forward. As for critics of The Garden of Ediacara, one of several books hes published, he says he was misunderstood and that some of its assertions were intended to show that researchers know much less than they think. But he maintains the belief that intellectual caution is not always whats needed, as he wrote back then.
And hes excited about the work to come, amazed at what we still dont know about Ediacarans. This is the appearance of complex life, he says. The planet at this point is already over 3 billion years old. Where had they been all this time? No one knows for sure, but more clues might lie just off the commuter rail.
Steve Macone is a freelance writer based in Boston. E-mail comments to firstname.lastname@example.org.