Anaximander believed that life began in the sea, and that by some type of adaptation to the environment, animals evolved into what they are today. He believed that the human species must have been born out of other animals, because we are far too vulnerable and reliant during infancy, and we could not have survived otherwise.
Empedocles also dealt with the first origin of plants and animals, and with the physiology of humans. As the elements entered into combinations, there appeared strange results—heads without necks, arms without shoulders. Then as these fragmentary structures met, there were seen horned heads on human bodies, bodies of oxen with human heads, and figures of double sex. But most of these products of natural forces disappeared as suddenly as they arose; only in those rare cases where the parts were found to be adapted to each other did the complex structures last. Thus the organic universe sprang from spontaneous aggregations that suited each other as if this had been intended. Soon various influences reduced creatures of double sex to a male and a female, and the world was replenished with organic life.
Lucretius also argued in favor of a theory of evolution. Lucretius laid out his evolutionary theory in his poem titled On the Nature of Things. He followed his predecessors by claiming that the earth gave birth to its creatures through a combination of elements. For Lucretius, the force that is responsible for life’s creations is chance.