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"There is no cure for birth or death save to enjoy the interval".
The quote, by poet and philosopher George Santayana, is a favourite of Dr Jilly Evans, who has spent much time considering our life-spans.
As keynote speaker at the sixth New Zealand International Science Festival in Dunedin, Dr Evans will give a public lecture titled "Ageing Well: Genes, Lifestyle and Medicines", on Monday.
Although she doesn't hold to the concept of a fountain of youth, Dr Evans does believe in the possibility of extending our end point.
Barring accidents and emergencies, death could be deferred, allowing humans to get closer to their full genetic potential of 110-120 years.
How? Well, medical intervention will play a key role. So, too, will lifestyle.
Thus the quality of our existence may very well determine the quantity of our time on Earth.
"We all have genetic potential to live to a certain amount, but given perhaps a very positive outlook on life, we can stretch that to the very fullest of whatever that genetic potential is," Dr Evans explains..
"Many of us have genes that would allow us to live to 85-90 or beyond, but perhaps things happen to us or lifestyle choices modify how long we go . . ."
There is a bell-shaped curve so there are people who live longer, Dr Evans says, pointing to the oldest woman of all time (according to the Guinness Book of World Records), Jeanne Calment, of France, who died on August 4, 1997, aged 122 years and 164 days.
The New Zealand biochemist, now based in San Diego as vice-president of biology for Amira Pharmaceuticals, will also highlight key medicines that have allowed people to live longer and how this intertwines with genetics and our environment.
Healthcare improvements, drug development, and stem cell and gene therapy will be discussed along with the importance of what she terms "best lifestyle practices".
There are many factors that determine longevity.
The scheduling of your final day could well be due to a combination of nature and nurture.
Dr Evans says there is a direct, though crude, correlation between an animal's body mass and its lifespan.
In evolutionary terms, mankind punches above its weight.
"If you look across all mammals, there is a line you can draw. Elephants can live to about 80 years.
Now, humans are bit smaller than elephants and we can live to about 110 . . .
We overachieve, but we can't achieve greatly beyond that because there are limitations, which are probably to do with metabolic rate and other things."
Though nature offers a genetic blueprint "which we can't do anything about", before you throw your hands up in the air in despair at the suggestion your day of death was decided as soon as sperm met egg, there are some strong escape clauses.
"The blueprint is there, but there is a big range in the potential you can reach in your blueprint, both in your physical health and your mental health," Dr Evans says.
"I think it is partly good healthcare, good medicine, good social activities and it is partly the luck of the genes you have whether you are going to get various illnesses later in life."
Nutrition, exercise (of the mind as well as the body), love, laughter, fun and friendship are other factors worth considering, Dr Evans says, adding it's important to have interests that keep you active, "so you can expand your horizons even as you're ageing".
"Often, that is what makes the difference between a good and, perhaps, lesser quality of life."
A warning: as dangerous as any strain of staphylococcus is stress.
It will shave years off your life.
"If you happen to have reasonably good genes and have lived a reasonably good lifestyle, you should be able to live, barring accidents, to 85 or 90 years.
"The people who seem to live on to 105-110, almost all of them have low stress levels - they don't get stressed by things. That stands them apart.
"I was reading about the oldest [living] woman in the world, who is 115.
"Her name is Edna Parker and she is in an old people's home in Ohio.
"Both her sons have died and she's been through lots of difficult life experiences, but it appears that she is an upbeat, positive person.
"I think she epitomises the type of person that can live to a really good old age."
But back to the start: birth, too, has a role to play in death.
In utero, there are "huge" hormonal and nutritional influences.
"The early years, which include in utero, are unfortunately a period you can't control. Those early years [to the age of 3] are really important.
"Those are the years you're interacting with your early infectious disease influences.
"The pattern of how you're going to respond is built in those early years."
Later in life, the choices you make can accelerate your mortality, Dr Evans says.
"Smoking is clearly extremely deleterious.
"You can look at people like Winston Churchill, who smoked a cigar every night and he lived to his 90s, but he might have lived to be 110 . . .
"Alcoholism is, of course, a very serious disease. The liver can only take so much alcohol.
"Certainly, if you are a confirmed alcoholic, you have shortened your lifespan as well, [although] a little bit of alcohol is good for you."
Love? Laughter? Fun? Dr Evans agrees such concepts are not usually associated with drug companies.
Yet here is a pharmaceutical biochemist who prefers a holistic approach to healthcare.
"I think we should use the best of all worlds of talents.
"If people really feel that their lives could be improved by some sort of therapy that is rather odd, I'm not against that," she says.
"I'm against people who fool others into something which isn't really correct.
"I'm very positive about meditation, acupuncture and herbal therapies - in caution, because herbs can kill.
"I'm a very optimistic person. I do believe hope is a very important thing.
"I had a friend die recently of ovarian cancer and I was sitting opposite her in a café a week before she died and she was saying to me, 'Jilly, I still think you can come up with something'.
"I wasn't going to, but the point is she had that gleam in her eye.
"We shouldn't take that away from people, but nor should we try to fool people."
Though the 55-year-old is described by her husband as "relentlessly optimistic", her feet remain grounded in scientific reality.
All hope aside, there are concrete reasons why the average lifespan in New Zealand has risen from 55 to 85 within the past century.
"Infant mortality has improved incredibly in New Zealand in the last 100 years" Dr Evans says, pointing to a number of factors, including vaccination programmes.
"The understanding, which was probably already there by 1900, that you had to have clean water, fresh sanitation . . .
I" would say antibiotic use, by 1950, was very common and that saved a lot of young lives.
"A lot of young kids died of regular bacterial infection and they no longer do.
"Used properly, antibiotics are clearly a huge boon for the world.
"Of course, they are going to have to make new antibiotics because bacteria are mutating.
"We can't stand still . . . because nature is not standing still. We have to fight new diseases and viruses."
That neck-and-neck race with nature is, in essence, what makes Dr Evans tick.
She admits it is a challenge.
Acute diseases, including cancers and cardiovascular illnesses, continue to kill, while chronic diseases such as arthritis and diabetes have dramatic impacts on quality of life.
And there are a number of infectious diseases that pose problems.
These include fairly common bacteria such as the methicillin-resistant Staphylococcus aureus (MRSA), which causes severe and sometimes fatal pneumonia; viruses such as respiratory syncytial virus and rhinovirus, which cause severe exacerbations of asthma and bronchitis; and the herpes virus, which causes diseases such as encephalitis, genital ulcers and shingles.
Dr Evans says science's progress is often done in small steps rather than huge leaps.
"Occasionally, a wonder drug comes up, but it's not very often. You could call antibiotics wonder drugs.
"I think that is fair . . . nobody thought you could take a pill and 10 days later be cured of a highly infectious bacterial disease.
"I don't believe there will ever be a wonder drug that allows you to live forever, and I'm not sure I'd particularly want to, [but] I do think there are wonderful improvements coming along for various diseases now that can allow people to live longer.
"Cancer is one example. The majority of childhood leukaemia is no longer fatal.
"The drugs are such that we can treat that and the majority of children will get through.
"There are other cancers, pancreatic cancer and so forth, that we don't have very good drugs for and we have to work harder on those things."
Born in April 1953, the same month Crick and Watson's ground-breaking double helix DNA paper was published in Nature magazine, Dr Evans claims she is not a "natural" scientist.
Still, by the age of 14 she'd fallen "in love with DNA" and understanding the basis of life.
"Until I was about 11, I had no huge interest in science. It was because of all these fabulous teachers that I got turned on . . .
"I remember writing an essay on DNA and RNA viruses when I was 16.
"I have continued to be extremely interested in the basis of not only human life but also the infectious disease life which is very much part of us as well."
Dr Evans returns to New Zealand at least once a year to visit her mother, a "very active" 80-year-old who lives north of Auckland.
She thanks her mum for much of her academic achievement.
"My mum, Julie Davis, was a kindergarten teacher. When you look back on it, her early childhood education of me set my potential.
"I could read, write and do my arithmetic way before I was five . . .
"I was very good at writing and thought I'd be an English or history teacher, but I had fabulous teachers who brought out my curiosity.
"I think that's what I'd like to do . . . engaging kids' curiosity so they will think about things around them and realise that everything is science."
Hear the talk
Dr Jilly Evans will present "Ageing Well: Genes, Lifestyle and Medicines" at 7.30pm on Monday, July 7, at the College of Education Auditorium, Dunedin.