Alcmaeon says that men die for this reason, that they cannot join the beginning to the end. (Aristotle Probl. 17, 3, 916a33)
Alcmaeon was a Pythagorean who lived probably in the 5th Century BCE. Information about Alcmaeon is limited to a handful of fragments attributed to him by Aristotle, Diogenes Laertius, and Aetius. Alcmaeon's theories took a medical approach to cosmology and natural philosophy. In the tradition of Pythagoras, Alcmaeon asserted that the world is composed of pairs of opposites - for example: Limit and Unlimited, Odd and Even. In men, the soul is an "attunement" of physical pairs of opposites that compose the body. Disease comes when one of these opposites is either deficient or in excess. Health likewise is the result of the appropriate balance of these opposites.
The quote from Aristotle above refers to Alcmaeon's doctrine of the soul. Heavenly bodies have the property of continuous circular motion. The souls of men are unable to remain circular, for man's time is finite; thus, men die. The doctrine of the circles revolving in the soul found in Plato's Timaeus seem to borrow from Alcmaeon's theory.
Alcmaeon's theory of finitude gains much relevence today in Heideggerian ideas of finitude and "being-towards-the-end."
Fragments from Alcmaeon can be found in: The Pre-Socratic Philosophers G. S. Kirk and J. E. Raven, Cambridge University Press (1957)