Previous: Chapter Seven: Wildlife Management
Frances and Jo approached the door of the Ranch’s Bioenginering lab. Frances knocked, gently and whispered to Bender, “Varley and Cass are their names. Varley’s a post doc, Cass is a grad student.”
A voice called out from the other side of the door. “Come in!”
Varley was logging the latest sample, using pencil and paper. Four sheets were fully covered. The handwriting alternated between Varley’s to Cass’s, reflecting that they’d worked around the clock in alternating four hour shifts. Each had checked and initialed the other’s data against the figures typed into the computer at the end of each shift. This was good work.
Varley turned from the sequencer to a the computer, and waved up the informatics screen. A complicated series of DNA bar graphs and sequence counts appeared.
“We teased out the mammalian chromosomes from the poop samples. Wallabies have the same XY sex determination system that we do, and like all eukaryotes, also have mitochondrial DNA which we only get from our mothers. So we can estimate the sex distribution, and also learn something about lineage.
“I think we’re looking at around 20 individuals. Pretty evenly mixed, sex wise. A surprising number of them, perhaps two thirds, are young. From mitochondrial DNA, we’re probably looking at their cohort sharing four or five adult mothers, and at least three of those were still alive and pooping, three weeks ago.”
Jo asked, “How young? What’s the age distribution on the young?”
Varley pulled up the graph. “This shows the pellet size distribution, which we measured with a camera and a light table.” The nose of Suse, the younger grad student, wrinkled at this.
“You can see there’s two islands of size distribution, corresponding to what we call Generation One and Generation Two. Our sample size is limited, but we think Generation Two has been out of the pouch for two or three months, which means they were born nine or ten months ago.
The locals in the room stiffened slightly. Nine months. Henrietta.
Frances murmured, “Where on earth could they have come from?” Then, aloud, to Varley, “Let’s see mitochondrial.”
Varley demurred. “Cass is Monarch of the Mitochondria. Cass?”
Cass brought up the data set, “This is a provisional matriarchal lineage based on the mitochondrial DNA of each individual. A family tree, showing mothers and daughters only. The offspring of Generation Two were linked to their probable mothers among Generation One. On the line above Generation One, ghostly predictions of probable ancestral grandmother relationships were indicated by vague outlines overlain by question marks and statistical probabilities. And on the top of that, projected down the generations with still more provisional uncertainty, a single X-greats-grandmother.
“We’re still working on Y Chromosome Adam, but this is “Mitochondrial Wallaby Eve.” She lived about thirty generations before her youngest descendants, Generation Two here in Texas. And she was probably born around…”
Suse, whose analysis it was, cut the senior grad student off: “Around 1950. I call her Wallab-Eve for short.”