The Guardian Human lifespan has hit its natural limit, research suggests news A study The Guardian The Guardian A study The Guardian A study The Guardian The Guardian A study Human lifespan 'has hit natural limit'... Human lifespan has hit its natural limit, research suggests news Human lifespan has hit its natural limit, research suggests A study Human lifespan 'has hit natural limit'... The Guardian Human lifespan has hit its natural limit, research suggests The Guardian A study Human lifespan has hit its natural limit, research suggests Human lifespan has hit its natural limit, research suggests The Guardian conclusiones Human lifespan 'has hit natural limit'... Human lifespan 'has hit natural limit'...