Absence of aging in hydra:<p><a href="http:&#x2F;&#x2F;www.pnas.org&#x2F;content&#x2F;112&#x2F;51&#x2F;15701.abstract" rel="nofollow">http:&#x2F;&#x2F;www.pnas.org&#x2F;content&#x2F;112&#x2F;51&#x2F;15701.abstract</a><p>&quot;Here, we present compelling evidence for constant mortality and reproduction of Hydra using data from careful, large-scale studies over 8 y with 2,256 individuals.&quot;<p>But really, you only have to point to the germline to note that aging doesn&#x27;t have to exist as a matter of basic physics. The germline, like hydra, regenerates itself - rejuvenation through proficient repair. If it didn&#x27;t, we wouldn&#x27;t exist.<p>Similarly for many species of bacteria. Some of them do age, but many do not, though once you go past yeast to bacteria you start to have definitions for aging that are quite distant from what it means in complex multicellular organisms like hydra or ourselves.<p>So thermodynamics and entropy is - and always has been - a pretty silly place to stand when looking at aging, as we can haul out any number of complex living systems that (a) don&#x27;t age and (b) absolutely follow the laws of thermodynamics, just like all of the rest of us.