Sex cells evolved to pass on quality mitochondria

Mammals immortalise their genes through eggs and sperm to ensure future generations inherit good quality mitochondria to power the body's cells, according to new UCL research. Before now, it was not known why mammals rely on dedicated sex cells that are formed early in development (a germline) to make offspring whereas plants and other simple animals, such as corals and sponges, use sex cells produced later in life from normal body tissues. In a new study, published today in PLOS Biology and funded by NERC, EPSRC and the Leverhulme Trust, UCL scientists developed an evolutionary model to investigate how these differences evolved over time and discovered that the germline in mammals developed in response to selection on mitochondria (the powerhouses of cells). First author and UCL PhD student, Arunas Radzvilavicius, said: 'There have been many theories about why mammals have a specialised germline when plants and other ancient animals don't. Some suggest it was due to complexity of tissues or a selfish conflict between cells. The distinction between sex cells and normal body tissues seems to be necessary for the evolution of very complex specialised tissues like brain. 'Surprisingly, we found that these aren't the reason.