Efforts To Expand The Lifespan Ignore What It’s Like To Get Old 

Critics:

Human beings and members of other species, especially animals, age and die. Fungi, too, can age. In contrast, many species can be considered potentially immortal: for example, bacteria fission to produce daughter cells, strawberry plants grow runners to produce clones of themselves, and animals in the genus Hydra have a regenerative ability by which they avoid dying of old age.

Early life forms on Earth, starting at least 3.7 billion years ago, were single-celled organisms. Such organisms (Prokaryotes, Protozoans, algae) multiply by fission into daughter cells, thus do not age and are potentially immortal under favorable conditions. Aging and mortality of the individual organism became possible with the evolution of sexual reproduction, which occurred with the emergence of the fungal/animal kingdoms approximately a billion years ago, and the evolution of seed-producing plants 320 million years ago.

The sexual organism could henceforth pass on some of its genetic material to produce new individuals and could itself become disposable with respect to the survival of its species. This classic biological idea has however been perturbed recently by the discovery that the bacterium E. coli may split into distinguishable daughter cells, which opens the theoretical possibility of “age classes” among bacteria.

Even within humans and other mortal species, there are cells with the potential for immortality: cancer cells which have lost the ability to die when maintained in a cell culture such as the HeLa cell line, and specific stem cells such as germ cells (producing ova and spermatozoa). In artificial cloning, adult cells can be rejuvenated to embryonic status and then used to grow a new tissue or animal without ageing.

Normal human cells however die after about 50 cell divisions in laboratory culture (the Hayflick Limit, discovered by Leonard Hayflick in 1961). Dementia becomes more common with age. About 3% of people between the ages of 65 and 74, 19% between 75 and 84, and nearly half of those over 85 years of age have dementia. The spectrum ranges from mild cognitive impairment to the neurodegenerative diseases of Alzheimer’s disease, cerebrovascular disease, Parkinson’s disease and Lou Gehrig’s disease.

Furthermore, many types of memory decline with ageing, but not semantic memory or general knowledge such as vocabulary definitions, which typically increases or remains steady until late adulthood. Intelligence declines with age, though the rate varies depending on the type and may in fact remain steady throughout most of the lifespan, dropping suddenly only as people near the end of their lives.

Individual variations in the rate of cognitive decline may therefore be explained in terms of people having different lengths of life.There are changes to the brain: after 20 years of age there is a 10% reduction each decade in the total length of the brain’s myelinated axons.

Age can result in visual impairment, whereby non-verbal communication is reduced, which can lead to isolation and possible depression. Older adults, however, may not experience depression as much as younger adults, and were paradoxically found to have improved mood despite declining physical health. Macular degeneration causes vision loss and increases with age, affecting nearly 12% of those above the age of 80.

This degeneration is caused by systemic changes in the circulation of waste products and by growth of abnormal vessels around the retina. Other visual diseases that often appear with age would be cataracts and glaucoma. A cataract occurs when the lens of the eye becomes cloudy making vision blurry and eventually causing blindness if untreated. They develop over time and are seen most often with those that are older. Cataracts can be treated through surgery. Glaucoma is another common visual disease that appears in older adults. Glaucoma is caused by damage to the optic nerve causing vision loss.

Glaucoma usually develops over time but there are variations to glaucoma, and some have sudden onset. There are a few procedures for glaucoma but there is no cure or fix for the damage once it has happened. Prevention is the best measure in the case of glaucoma. A distinction can be made between “proximal ageing” (age-based effects that come about because of factors in the recent past) and “distal ageing” (age-based differences that can be traced to a cause in a person’s early life, such as childhood poliomyelitis).

Ageing is among the greatest known risk factors for most human diseases. Of the roughly 150,000 people who die each day across the globe, about two-thirds—100,000 per day—die from age-related causes. In industrialized nations, the proportion is higher, reaching 90%. In the 21st century, researchers are only beginning to investigate the biological basis of ageing even in relatively simple and short-lived organisms, such as yeast.

Little is known of mammalian ageing, in part due to the much longer lives of even small mammals, such as the mouse (around 3 years). A model organism for the study of ageing is the nematode C. elegans – having a short lifespan of 2–3 weeks – enabling genetic manipulations or suppression of gene activity with RNA interference, and other factors. Most known mutations and RNA interference targets that extend lifespan were first discovered in C. elegans.

The factors proposed to influence biological ageing fall into two main categories, programmed and error-related. Programmed factors follow a biological timetable that might be a continuation of inherent mechanisms that regulate childhood growth and development. This regulation would depend on changes in gene expression that affect the systems responsible for maintenance, repair and defense responses.

Factors causing errors or damage include internal and environmental events that induce cumulative deterioration in one or more organs….