puits (1) biologie (1) marsupiaux (1) mammifère (1) génétique (1) gène (1) exportation (1) différenciation (1) datation (1) Differentiation (1) Genetics (1) Dating (1) Observations (1) Observations (1) Housekeeping (1) Genes (1) Origin (1) X chromosome (1) Sex chromosomes (1) Sex (1) Meiosis (1) Human beings (1) Mammals (1) Hypothesis (1) Genetics (1) Gene expression (1) Expression (1) Driving of horse-drawn vehicles (1) Chromosomes (1) Biology (1)