Living to a ripe old age

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Biology / Botany / Evolution / Health / Zoology

When I was a kid, I aspired to live to 100 so I could get my letter from the Queen. These days I have a rather different view of the monarchy and more insight into the pivotal role of good health in old age. Of course that hasn’t changed the fact I hope to live to a ripe old age. But once you start to consider other living things, you realise our human longevity record of 122 years and 164 days is piffling. If you want to talk old age, there are a plenty of other animals and plants with lifespans far more impressive than ours. The question is: why do some things live so much longer than others?

What's the secret to old age? And why do some creatures live much, much longer than others? Image credit: Sean Mason via Flickr (original artist unknown)

What’s the secret to old age? And why do some creatures live much, much longer than others? Image credit: Sean Mason via Flickr (original artist unknown)

The old age all-stars

Have you heard of Ming the mollusc? Possibly not, but in the context of old animals, Ming is a super star. Ming’s a deep-sea clam also known as an ocean quahog and was named after the Chinese Dynasty in power when it was born. Yes, scientists have calculated Ming was 507 years old. Was because Ming had to be killed to be part of the scientists’ study. You can age an ocean quahog by counting the rings on its shell but the animal dies in the process.

If 507 sounds old, how about deep-sea corals that have been recorded to be more than 4,000 years old? There are also marine sponges living in Antarctica that have been clocked at 1,550 years.

Back on land, Harriet the Galapagos tortoise was supposedly collected by Charles Darwin in 1835 and arrived in Australia in 1842. She lived for more than 100 years in the Brisbane Botanical garden and ended up at Australia Zoo where she was said to have been 176 when she died. Another tortoise, a pet of the Tongan Royal family, Tu’I Malila was known to be 188 at death.

When it comes to mammals, the endangered bowhead whale has been given the title of longest-lived. Bowhead whales live in the Arctic and are the second heaviest whales after blue whales.

Researchers have recently looked at the bowhead whale genome to see what they can learn about the secrets of long life. Clear evidence of their long lifespan came when a stone harpoon tip was recovered from inside the neck of a bowhead whale in 2007. The harpoon tip was dated to 1880, which means this whale was at least 130 years old. In fact, scientists believe these whales live to 200 years.

Plants do it even better

There are many claims the oldest known individual tree is a Giant Basin Bristlecone Pine, still alive and currently aged 5,065 years. But Rachel Sussman, author of The Oldest Living Things in the World says there is an Antarctic Beech tree in Lamington National Park here in Australian that is 6,000 years old.

Then there are clonal trees. The Pando quaking aspen grove is a colony of trees covering 43 hectares in Utah that is estimated to be 80,000 years old. To be clear: it is the single root system that has been alive for that long. Each of the 47,000-odd genetically identical stems are probably only 75 – 200 years old.

To put things into perspective: the Pando colony was around before humans had even arrived in North America. Right now, the colony weighs 5900 tonnes and is officially the heaviest living thing we know about on the planet. (Note that the largest living thing on Earth is a fungus).

And in case you haven’t been sufficiently impressed by the plants yet, how about a colony of seagrass living in the Mediterranean that includes patches which are 200,000 years old?

Immortality, anyone?

Remember Benjamin Button who lived his life backwards – starting old and ending young? Scientists have found a jellyfish that lives its life in a similar way. It effectively recycles itself, going backwards from an adult stage to an immature stage over and over again.

There is also a freshwater animal called a hydra that can self-renew and regenerate. By renewing their old cells, these tiny animals are thought to be able to live to 1,400 years.

These animals are just about as close to immoral as we’re ever going to find.

Old ain’t old

The question is: why can’t humans get much beyond 120 years whereas a whale can live to 200 years? Why is extreme old age so variable among different species?

We used to think it was fairly straightforward: an animal’s lifespan is roughly proportional to its body weight and heart rate. A big slow elephant will live for a much longer period than a small fast mouse. But birds and bats, although small, tend to live longer than many bigger animals and Ming shows small animals can live for a very long time.

Scientists still puzzle over why we see such a huge variety of ageing rates among living things. There are almost certainly genetic factors involved, and research has shown the way different species are able to repair bodily damage may be important.

Regardless of the reason it’s hard not to feel a little wistful about the way we humans are impacting Earth. We are changing the face of the planet in such a relatively tiny amount of time compared to the lives of some of the plants and animals we share it with.

Links and stuff

Radio on demand

 This post accompanies a radio segment on Triple R’s Breakfasters program on Wednesday 20 May 2015. 

5 Comments

  1. Poor Ming – I hadn’t heard of Ming, but knew of Harriet. Your closing words are unfortunately oh so true.

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