Starting closer to us, human centenarians (living over 100 years) have been studied to determine what characteristic biologic factor(s) leads to long life. These people are a very widely varying group. Diets of these centenarians  have considerable variation with no food outstanding as a common source of their longevity. Some smoke, some drink, some are good tempered, and some are mean as nails. Cholesterol levels vary considerably. The oldest ever recorded (well documented) was Jean Calumet of France who died at 122 years of age. She smoked and drank all of her life until about 100 years of age. She claimed that chocolate had kept her alive so long. We can set the maximum human life span by this 122 years of age, as we have no other documented examples of greater human life span.

The only common finding shared by all centenarians(besides being from relatively long lived families is 1.) a very well preserved insulin response to rising dietary incoming blood sugar with a rather Low Body Mass Index (=weight divided by (height)^2 in kilogram/meter system-meaning that they were relatively slim) AND 2.) a much lower rate of chronic inflammatory activation with age .

You can calculate your own BMI at the NHBL site. Notice that too high a value and too low a value are both considered less healthful.

This absence of age adjusted higher levels of resistance to insulin and lower chronic inflammation levels in centenarians is critical.

This better handling of glucose compares to the far more common finding of a continual rise in insulin resistance with rising fasting insulin levels and some rise in fasting blood glucose levels in normal middle aged humans. Insulin sensitivity and insulin resistance are both focused on the ability to handle an increased level of glucose entering the blood stream from meal with low insulin levels (low insulin resistance = high Insulin sensitivity). Conversely, very high blood circulating insulin levels are harmful. High insulin resistance  in response to rising blood sugar means that cells are not as sensitive to low level of insulin to absorb the blood sugar. This forces the body to produce and release into the blood stream much more insulin. Insulin resistance means the body does not efficiently remove glucose from the blood stream. Higher blood stream levels of glucose damage proteins by complex free radial mechanisms. AIn addition to better control over glucose by low levels of insulin, centenarians also have lower levels of blood circulating triglycerides (triglycerides are are the typical fats and oils we buy in the market). Centenarian's levels of insulin and triglyceride have risen over life, just like other people, but not as much as others. Notable among centenarians is the post mortem finding of virtually no evidence of Alzheimer's disease or similar dementia manifestations ( http://www.allbusiness.com/professional-scientific/scientific-research/258199-1.html ).

What researchers are finding from these major centenarian studies is that there is hardly anything in common among these people. They have high cholesterol and low cholesterol, some exercise and some don't, some smoke, some don't. Some are nasty as can be, some nice and calm and some are ornery... But, they all have relatively low sugar for their age, and they all have low triglycerides for their age... And, they all have relatively low insulin... If there is a single marker for lifespan, as they are finding in the centenarian studies, it is insulin, specifically insulin sensitivity. Low Grain and Carbohydrate Diets Treat Hypoglycemia, Heart Disease, Diabetes Cancer and Nearly ALL Chronic Illness    Joseph Brasco, MD     

In conclusion, our study demonstrates that centenarians compared with aged subjects had a preserved glucose tolerance and insulin action." Glucose tolerance and insulin action in healthy centenarians   G. Paolisso, A. Gambardella, S. Ammendola, A. D'Amore, V. Balbi, M. Varricchio and F. D'Onofrio   Am J Physiol. 1996 May;270(5 Pt 1):E890-4  

...studies comparing adults of various ages with centenarians on various aspects of body composition and insulin action found that centenarians had a lower body mass index, lower levels of body fat, lower plasma triglycerides, and lower indicators of oxidative stress(Barbieri et al. 2003;Paolisso et al. 1997). Centenarians also had a higher insulin sensitivity than that of much younger adults (i.e., their insulin resistance was much lower). Although the centenarians had low absolute levels of insulin like growth factors (IGF-1), their levels of active IGF-1 (i.e. not bound to a transport protein) was higher than that of aged adults (75-99 yrs) but lower that that of younger adults < < 50 yrs). Thus, the possibility exists that these centenarians have somehow preserved their IGF-1 and insulin sensitivity.   The Biology of Aging (1998)  Robert Arking  

The way to treat virtually all of the so-called chronic diseases of aging is to treat insulin itself... Insulin resistance is the basis of all of the chronic diseases of aging, because the disease itself is actually aging. Insulin and Its Metabolic Effects Ron Rosedale, M.D.   

The gradual age-related decline in physiologic function and the late life exponential rise of a diverse group of age-associated diseases are explained by imbalance in specific hormonal axes and cumulative growth factor exposure, respectively. Nutritionally driven 'normal' insulin exposure is central to both cumulative growth factor exposure and imbalance of the insulin-growth hormone axis. Halving normal young adult insulin levels by increased insulin sensitivity may slow the aging process. Insulin exposure controls the rate of mammalian aging.  Parr, Tyler   Mech Ageing Dev. 1996 Jul 5;88(1-2):75-82.   

The present nationwide census-based study of Japanese centenarians found that 10.4% centenarians were autonomous centenarians, in other words, had preserved ADL, cognitive status, and psychosocial status. In this study, such centenarians were considered to be models of successful aging.http://onlinelibrary.wiley.com/doi/10.1111/j.1532-5415.2006.01019.x/full
The Japanese Centenarian Study: Autonomy Was Associated with Health Practices as Well as Physical Status
1. Akiko Ozaki RN, PhD1, Makoto Uchiyama MD, PhD2, Hirokuni Tagaya MD, PhD4, Takashi Ohida MD, PhD3, Ryuji Ogihara MD, PhD5
Article first published online: 12 DEC 2006  J Amer Geriat Soc Volume 55, Issue 1, pages 95–101, January 2007

While most centenarians show various levels of age associated diseases, some CENTENARIAN humans show no known diseases of age that are common in much younger humans. Now we are beginning to realize that we are PREMATURELY dying by an INFLAMMATION driven age-associated diseases is not necessary.

This also applies to the high fat (modest or minor to major obesity) driven insulin insensitivity (typically type 2 diabetes) that generates elevated inflammatory levels that then further worsens the type 2 diabetes in to an ever worsening condition while also accelerating the dev elopement of all the other age-associated diseases. What is AMAZING is that it does not take much increase in "inside the belly fat" to begin this process, then it amplifies on its OWN ! This is not "NORMAL AGING", but it is the commonplace in all animals who can eat as much as they want. This was never factored into evolution because wild animals are almost never obese unless they live in extremely cold climates where this is a survival necessity. The food bounty of civilization that is enjoyed by humans and domesticated animals is almost unheard of in wild nature. Nature is much more cyclic abundance and dearth of nutrition. Under the lucky unusual conditions when abundant food was present for the life of a wild animal (say early colonizers of a food rich, competition low environment), the animals offspring would have a shorter life span by epigenetic changes as we have examined in the ORIENTATION section table of article blurbs.