In our youth we are strong and healthy and then we weaken and die -- that's probably how most would describe what aging is all about. But, in nature, the phenomenon of aging shows an unexpected diversity of patterns and is altogether rather strange, conclude researchers from The University of Southern Denmark. Not all species weaken and become more likely to die as they age. Some species get stronger and less likely to die with age, while others are not affected by age at all. Increasing weakness with age is not a law of nature.

Researchers from the University of Southern Denmark have studied aging in 46 very different species including mammals, plants, fungi and algae（藻类）, and they surprisingly find that there is a huge diversity in how different organisms age. Some become weaker with age -- this applies to e.g. humans, other mammals, and birds; others become stronger with age -- this applies to e.g. tortoises and certain trees, and others become neither weaker nor stronger -- this applies to e.g. Hydra, a freshwater polyp（珊瑚虫，水螅虫）.

"Many people, including scientists, tend to think that aging is inevitable and occurs in all organisms on Earth as it does for humans: that every species becomes weaker with age and more likely to die. But that is not the case," says evolutionary biologist and assistant professor Owen Jones from the Max-Planck Odense Center at the University of Southern Denmark .

He is the lead author of an article on the subject in the scientific journal Nature. Other authors are from the Max Planck Institute for Demographic Research in Rostock, Germany, the University of Queensland in Australia, University of Amsterdam in Holland and elsewhere.

Owen Jones and his colleagues studied aging in species ranging from oak trees, nematodes（线虫）, baboons（狒狒） and lice to seaweed and lions. The species included 11 mammals, 12 other vertebrates, 10 invertebrates, 12 plants and one algae.

"The diversity of mortality and fertility patterns in these organisms surprised us, and there is clearly a need for more research before we fully understand the evolutionary causes of aging and become better able to address problems of aging in humans," says Owen Jones.