  The priority of the eternal celestial revolutions, furthermore, guarantees the causal finitude of the universe. This is so, even though there are infinite causal chains: behind every single individual of an animal species there is an infinite series of male ancestors, each causally responsible for the subsequent members in the series, because Aristotelian species are eternal and male parents are the efficient causes of their  offspring.[36]  Left to its own devices, the finite universe on its own would certainly reach a dissolution, a state of complete separation of the elemental masses into their concentrically arranged natural places. In view of the fact that such a complete segregation of the elemental masses is avoided through the constant excitation caused by the celestial motions, producing heat in the sublunary domain, especially around the regions of the  Sun,[37]  Aristotle will be entitled to assert that the cause of the human being is in the first instance his or her father, but is at the same time the Sun as it moves along its annual ecliptic  path.[38]  Between celestial revolutions and the individual natural processes there is always a finite causal chain, as these natural processes could not possibly have continued without the celestial motions.  The infinite causal chains passing through male parents cannot subsist on their own without this constant external support, and this dependence can always be analysed in terms of finite causal chains.