Sunday, January 10, 2010

(NSFW) Evolutionary Muscles, Skin, Fat

Fascinated Remix
(Offer Nissim, Courtesy of

Questionable Trade-Off Between Sex and Longevity

I've wondered about this dichotomy -- can humans and other mammals have both sex and longevity? Nick Lane, author of Life Ascending, gives his deep, refined thoughts on this apparent contrast. 'The idea of a trade-off between sex and longevity was laid out by the British gerontologist Tom Kirkwood pictured exactly such a 'choice', on the economic grounds that ENERGY is limited and everything has a cost. The energetic cost of bodily maintenance must be subtracted from the energetic cost of sex, and organisms that try to do both simultaneously will fare less well than organisms that apportion their resources...'

This change that occurred in evolution when mammals internalized pregnancy and increased child-rearing from a few weeks to a few years may explain how the priorities in energetics shifted. It reminds me of other predators... bears, wolves and coyotes. Just like them, we invest a great deal of resources into teaching, reinforcing, enrolling into chest club, swimming lessons, golf camp, piano lessons and other preparations necessary for optimal success in life. Actually we invest VERY LITTLE in sex but MUCH MUCHO MORE in maintenance phases. The higher up the supposed predator food chain, the balance is FAR shifted toward maintenance phases, less sex. Nick Lane's theory is that 'In all cases, though, there is a choice, and in animals that choice is normally controlled by the insulin hormones.'

Behavioral budgeting by wild coyotes: The influence of food resources

Coyotes and wolves are quintessential survivors and clever companions. Dogs are pretty close. My daughter is reading a wonderful series called 'Wolf Brother' by Michelle Paver.

Coyote populations display a very curious 'negative relationship between coyote abundance and population growth' as these authors noted. Though increased litter size occurs with food abundance, 'There was also a hint that mean litter size may be correlated with food conditions under which females are reared, as opposed to conditions leading up to specific reproductive seasons (Knowlton and Stoddart 1983).'


Energy balance of the female of the species explains a lot. Certainly gender-specific nutrigenomics play a role. We are definitely more sensitive to the insulin resistant, pro-inflammatory effects of glucocorticoids and n-6 PUFAs than our male counterparts. Vitamin D (e.g. duration photoperiods), probably as well, esp if you believe the female-forager theories and division of labor.

Prior post (read end): n-6 PUFAs Cause Inflammation and Cancer: Israeli Experience

Energy Balance: Relates to Priorities in Mammalian Physiological Functions (SEX v. maintenance v. decreased population growth)

Bronson describes energy balance affecting reproduction in all animals. If the priority is survival and forwarding genetic material to the next generation, this all makes incredible and wonderful sense. Everything appears clear in light of evolution.

Climate change and seasonal reproduction in mammals. PDF free.

Evolutionary Skin

Recently, I started bikram yoga and... oh boy. It's H-O-T. One hundred four degrees F to be precise, in 40% humidity which grows during the 90min sessions. Skin is a big excretory organ (bigger than the KIDNEYS... *wink*). Sweating is a stellar way to detox whether it is during exercise or in a sauna -- the Japanese and Korean spend a lot of time in sauna-like hot baths; the Greeks luxuriate in hot mineral baths. After the class starts, within 5-10min every person in the room is dripping bodily fluids. Every sweat gland gets a workout. Even. My belly button's. In fact, it's gross but I discovered my knees SWEAT too.

Under My Skin: Subcutaneous Fat

Subcutaneous fat stores are anatomically located under the skin. Pinch an inch or grab a slab? (after holidays, the later for me) The quantity and quality of our storage fat and skin fluxes with the same hormones that affect our muscles.

See NephroPal: Evolutionary Muscles and Skin

Heat Shock Hormesis

I've discussed hormesis and how cold showers relate in an earlier post. Being BIONIC. This winter I've enjoyed much less cold showers... which last... OHHHH... ~1.4 seconds long. *haa*

Hot bikram yoga is a much more preferable way for me to achieve hormesis because both cold and heat shock induce mTOR changes.

More Hormesis

Skin is our largest organ (yes, it is). Surface area ~ 27 sq ft (2.5 sq meter) and weighs about 9 lbs. Each square inch contains about 230 ft (70 m) of nerves and 16 ft (~5 m) of blood arteries and veins. More vitamin D synthesis occurs in our skin when we are heated (no sunlight involved, just temperature factors alone). According to the below authors "The skin locally synthesizes significant amounts of sexual hormones with intracrine or paracrine actions. The local level of each sexual steroid depends upon the expression of each of the androgen- and estrogen-synthesizing enzymes in each cell type, with sebaceous glands and sweat glands being the major contributors." I think we can have it both ways... sex/hormones... and quality, disease-minimized lifespans... (1) controlling insulin (2) keeping mitochondria happy. Hormones and hormesis are indeed key players for power, sex and survival.

Sexual hormones in human skin.


epistemocrat said...

Hi Dr. BG,

I second this:

"Sweating is a stellar way to detox."

And, thermal fluctuation hormesis takes the following forms for me: pool + hot tub + sauna + steam + cold/hot showers following exercise bouts at the gym (which include my self-created 'dynamic yoga' work, sans the 104 temperature!).

It's been a hormesis-filled hibernation winter for me. Quite enjoyable.



Dr. B G said...


That is quite inexcusably AWESOME! Yeah, I like your yoga moves...