The Age Ceiling

“The immortal jellyfish can revert from adult to juvenile and back again”

The immortal jellyfish Turritopsis dorhniiAs ageing becomes one of our biggest concerns, George Merrin examines what the upper limit of ageing is for other species.We like to think that we are the most advanced species due to our intelligence and our global domination. At a quick glance, this may be true, however despite all of our technological advances we still age and die. The oldest verified person ever was 122. This is nothing compared to other species. The oldest verified land based animal was a radiated tortoise named Tu’i Malila who died at 188. Radiocarbon dating has recently revealed a Greenland shark to be even older when a female was found to be about 400 years old. This species reaches sexual maturity at 150, redefining what we thought we knew about ageing in vertebrates. The previous record holder for vertebrates was a bowhead whale estimated to be 211 years old.Ageing is caused by the breakdown of the cell’s ability to correctly reproduce. This leads to cellular senescence, which is when division stops. This ultimately leads to death. As DNA reproduces, some is lost every time, which causes ageing. But not in all species. Lobsters seem to deal with senescence far better than we do and the immortal jellyfish can revert from adult to juvenile and back again.Aquatic invertebrate animals live longer than terrestrial or land based ones. Sponges such as Xestrospongia live for more than 2300 years and one Leiopathes coral was determined to be 4265 years old. We hardly exist in comparison.Most animal species don’t live for more than two hundred years whereas many plants live far longer. Many large species of plants live for thousands of years by forming interconnected root systems known as colonies. An example of such a system, Pando, is a quivering aspen found in Utah. Due to the nature of the organism it is hard to determine exactly how old it is. Most agree that Pando is around 80,000 years old, but some suggest that it may be closer to one million years old.Individual trees can still live for thousands of years. The oldest non-colonial tree currently known is a Great Basin Bristlecone Pine found in the USA. This tree is 5066 years old which means that it is older than the pyramids of Giza, while Stonehenge would have been 57 years old when it was planted.  The oldest tree in Europe is the Llangernyw Yew found in Wales. It is believed to be between four and five thousand years old.  Fungus can also survive for long periods with the“Humongous Fungus”, member of the Armillaria solidipes species, believed to be around 2400 years old.Endoliths are also among the oldest living organisms. They are microscopic and live in rocks, living off the minerals found there. They live for over ten millennia due to their slow metabolisms. Most of their time is spent repairing DNA damage, one of the factors which cause ageing.But how does this all relate back to us? Attempts are being made to investigate whether or not humans can undergo gene therapy to become biologically immortal, or extend our lifespan. With current life expectancies increasing, some scientists are even questioning if we will evolve this ourselves.