Largest, oldest creature on Earth?

I took a circuitous route to a conference in Salt Lake City. One of my stops was in south-central Utah at Fishlake National Forest, home to a trembling aspen (Populus tremuloides) grove that we 20th Century humans call “Pando” (meaning “I spread” in Latin). The aspen probably has another name for itself. The root system of Pando may be eighty thousand years old, about thirty or forty times as old as Latin.

This aspen grove covers about 44 hectares (108 acres) and is comprised of one “individual.” Through clonal growth, a founder seed has spread, amoeba-like, over the mountainside to create a forest of nearly fifty thousand stems, which look separate, but are in fact a single organism. The grove is reputed to be the heaviest and oldest creature on the planet, although some fungi likely nudge the aspen out of first place.

The story is not quite as simple as I have described, though. Through a few mutations in the clone (for biojargon lovers: somatic mutations) and perhaps a little sex, the spreading tree has managed to diversify its genetics. Like other big aspen clones, Pando also has an extra set of chromosomes (making it “triploid” instead of the usual “diploid”), all strategies that may have allowed it to defy one of ecology’s more rigorous rules: huge genetically uniform clones don’t last long in the face of environmental stress and disease (e.g., monocultures of agricultural clones are helped along by pesticides and herbicides; if left alone, they’d be eaten alive by fungi, viruses, and bacteria).

When this tree germinated, modern humans were found only in Africa (or so many think, our travel dates are hazy). The last ice age was just getting going. Now, though, the world is truly changed. Heavy grazing by cattle on National Forest land mows new sprouts (cows and their dung pats are everywhere); deer are also abundant. Humans have changed the rhythms of fire and animals. So, the old feller (yes, he’s a male clone), is now in a zoo-like exclosure fence and land managers are encouraging new sprouts to grow by cutting older trees. A flush of new growth has emerged from one of these zones.

He-whose-name-we-do-not-know is being taken firmly in hand, gardened and managed, by the recently-arrived primates from Africa. Check back in 80,000 years to see who is still around.