What is the last common ancestor?
If you suddenly find yourself in the company of paleoanthropologists or swamped by news of the latest hominid fossil find, there’s a good chance you’ll hear the phrase last common ancestor (LCA). In some circles, they throw the term around like it’s the Holy Grail or a winning lotto number. What is this enigmatic person or thing? The answer comes down to evolution and the way we plot its course through varying species. But let’s take a step back from the quagmire of natural selection for a moment and tackle this completely made-up concept: last common teacher. Think back to someone you went to school with for a period of time — maybe a childhood friend or even a college chum. You shared this teacher, that teacher — but what was the last teacher you both studied under bef
