Some considerations on the nature of LUCA, and the nature of life.

In addition to its scientific interest, research on the last universal common ancestor (LUCA) and the lower part of the tree of life raises important and difficult issues in biology, but also in the philosophy of science as well as in philosophy in general. The way inquiries are formulated has to be scrutinized to avoid unanswerable questions. Preconceived ideas, poorly defined notions and abuse of metaphors are obstacles which can induce bias in studies and in the interpretation of their results. In the background, the question of life has recently re-emerged.