People are always asking me for the source of those nice t-shirts that illustrate how long we’ve diverged from a given species. I think the name must be hard to remember: they’re at Now there’s a little software widget that will be just as neat-o.

Look up TimeTree, and remember to show it to the kids. This is a page with a simple premise: type in the name of two taxa (it will accept common names, but may give you a list of scientific names to narrow the search), and then it looks them up in the public gene databases and gives you a best estimate of how long ago their last common ancestor lived.

Grasshoppers and I, for instance, shared a many-times-great grandpa 981 million years ago. My zebrafish and I are practically cousins, with our last shared ancestor living a mere 454 million years ago. Hey, tree, we’ve been apart for 1407 million years, how’s it going? Sparrow! Long time no see! 325 million years, huh?

You get the idea. It’s great for getting the big perspective. The kids will pester you all the time for dates. Especially since…it’s got an iPhone app! Get on the App Store on your smart phone or iPad and search for TimeTree — it’s totally free (except for the cost of owning such a gadget, of course).

Oh, and once you’re done entertaining the children and yourself, it’s actually a serious tool. Tap on the results and it’ll take you to all the scientific details: breakdown of mitochondrial vs. nuclear date estimates, source papers, all that sort of thing.

For details on how it works, there’s also a published paper:

Hedges SB, Dudley J, Kumar S (2006) TimeTree: a public knowledge-base of divergence times among organisms. Bioinformatics 22(23):2971-2972.

Look, a cat! 92 million years.