The yin and yang of reproduction

The trio of sex, multiplication and dispersal are the pillars of the evolution of life on Earth. Multiplication comes through the processes of sex and dispersal but requires neither. Many organisms reproduce only, or mainly, asexually and have no special mechanisms for dispersal. For organisms living in water, dispersal was never much of a problem. Water currents dispersed them haphazardly. But dispersal on the land is a formidable challenge, a cliff that the first land colonists had to scale. The landscape was only patchily friendly and even if a foothold could be established the leap from one damp patch to another was a huge challenge. The plants that first met this challenge, and the structures they used to do it, their spores, provide the first record of complex terrestrial life. In colonising the land, plants transformed it making it an easier place for other colonists.