Here On Earth: An Argument For Hope

by Tim Flannery

One of the iron-clad rules of physical evolution is that individuals cannot pass on to their offspring any favourable traits acquired during their lifetimes. Lamarck believed that giraffes could stretch their necks by continually reaching up for leaves, and that such stretched necks could be passed on to their offspring. Today we know that neck length among giraffes is coded in their genes, and that, with some rare exceptions (such as lengths of DNA inserted into genomes by viruses), physical traits acquired during an individual’s lifetime cannot be passed on. Cultural evolution, in contrast, is purely Lamarckian. It is fuelled by the spread of ideas, and technologies that flow from such ideas, and those acquired by one generation are passed on to the next. Cultural evolution is far faster than physical evolution: it took the sabre-toothed cats millions of years to evolve their great stabbing canines, but it took humans only a few thousand years to develop metal daggers that are far more potent weapons.