It's been about 60 days since Dr. David Tank rocked my world.
By showing me photos of leaves.
Like most of the 1,000 or so attendees of the Botany 2012 conference in Columbus, OH, I was spending the day taking in dozens of 15-minute talks given by the best and brightest in the plant sciences. And then, while moving briskly between sessions, I felt a hand on my shoulder.
"I need to show you something," said Tank, an Assistant Professor at the University of Idaho, "Come sit with me for a minute."
Before I could manage an "Okay," Dave had his laptop open and was showing me something truly unbelievable, even for a botanical optimist like myself. Shining brightly on his screen were images of whole tree leaves being peeled from the surfaces of 15-million-year-old rocks. I did a double take.
"Wait, the leaves, themselves, are 15 million years old? And you can hold them in your hands?"
Encountering these leaves, preserved in layers of rock since a period known as the Miocene, isn't exactly like finding an actual dinosaur (most of them vanished 65 million years ago) -- but it's pretty close. If what Dave was telling me was true, it's more like finding the flexible snout of a gomphothere (a long-extinct, elephant-like beast) with the hair and skin still intact. Simply outrageous.
I had to see it (in real life) to believe it. So, a couple of weeks later I went to Idaho with Paul Frederick and Tim Kramer, my co-producers on the video series, Plants Are Cool, Too!
There, in a fossil deposit on the edge of Clarkia, Idaho's aptly named Fossil Bowl Race Track, Dave and his colleagues showed me the real thing. Armed with nothing but pocket knives, they split open layers of ancient sediment that had settled in a volcano-induced lake millions of years before anything human-like walked this Earth. Stuck between those hardened layers were hundreds and hundreds of exquisitely preserved leaves.
The leaves are representative of a forest that is totally unlike anything in Idaho (or anywhere else) at present. Some of the leaves came from trees that were close relatives of species found today in the southeastern U.S. (like bald cypress) or central China (like dawn redwood), while others have no extant kin. No matter. They were all standing there in (what is now) Idaho 15 million years ago, as evidenced by the presence of their long ago fallen leaves in the rocks.
Let me state that again, somewhat differently: The trees last stood 15 million years ago, but their leaves are still here! The actual leaves, un-decomposed, with many of them sporting the fall color they had when ancient autumns brought them flitting down from their limbs to sink into the deep, cold waters that would help to preserve them for eons.
As one might imagine, these ancient biological specimens offer all sorts of potential for research. For example, Dr. Bill Rember, also of the University of Idaho, is looking at the leaf surfaces and measuring the densities of tiny pores used for gas exchange (called stomata) relative to what we see in today's leaves. Because stomatal density changes predictably with levels of atmospheric carbon dioxide, Bill can infer what those levels looked like in the Miocene -- a time when the Earth was in a period of global warming -- and use this to better understand what might happen as we continue to pump CO2 into our present atmosphere.
While the work on stomata is fascinating, the Clarkia-related research direction that is the most "Hollywood" might be the one that Dave Tank and his lab are heading in: extracting crazy-old DNA from those crazy-old leaves. As much as we might refer to Jurassic Park as an example of ancient DNA recovery, the truth is that we have never had much success in retrieving genetic material older than about 1 million years. The Tank Lab is seeking to change that by employing the same rigorous methodologies used by scientists who pull DNA from ancient human remains. And, so far, it appears to be working.
So, Dave was right. He certainly had something cool to show me. And in a few months, his lab could be offering us the chance to look over genetic blueprints that are orders of magnitude older than almost anything we've ever perused.
That's about as cool as it gets.
Plants Are Cool, Too!, Episode 2: Fossilized Forests:
Dr. Chris Martine is the David Burpee Chair in Plant Genetics & Research and Director of the Manning Herbarium at Bucknell University. He also is the creator, host, and co-producer of Plants Are Cool, Too!, a video series dedicated to highlighting the coolest plants on Earth (and the botanists who study them), with support from the Botanical Society of America.