Higher body Tps (esp. higher nerve & muscle Tps) allow faster reactions: for every 10°C, the velocity of the biochemical processes is more than doubled. Fast reactions are important for fighting rivals, catching prey, escaping predators, and in birds for flying. Generally speaking, the higher the nerve & muscle Tp, the better. But the costs of keeping body tissues at 40°C or more during the day are enormous. The energy expenditure of endotherms is several times that of ectotherms. Probably, Tps >40 or 41°C have other disadvantages: lipid solubility, protein denaturation, cell functioning etc. The highest known Tp in a living vertebrate is almost 48°C in the desert iguana. Desert birds have normal Tps between 39 & 42°C, and the domestic chicken can sustain a body Tp of 45°C for longer periods. Among mammals, the oryx can withstand a core Tp of 45°C, and Grant’s gazelle 46.5°C for many hours. But in humans, a rectal Tp of only 41°C may result in permanent brain damage (Chatton 1981:1,939).
Most mammals that heavily rely on speed for survival (e.g. most middle-sized terrestrial mammals) have body Tps of at least 38°C, lower in the morning & after resting, higher in the evening & after exercise, e.g. horses 38°C, cattle & guinea-pigs 38.5, rabbits, sheep & cats 39, goats 39.5°C (Slijper 1958:359). Several small mammals that do not defend themselves by running away may have lower body Tps, e.g. hedgehogs, mole-rats, monotremes, pottos, sloths normally from 30 to 35°C, so they have much lower energetic expenditures than other mammals of the same diet. Small semi-aquatic mammals in temperate climates like minks or muskrats (weighing c 1 kg) have almost 40 & 38°C on land, but in the water the body Tp drops to <35°C after 20 minutes, so these mammals have to come on land every few minutes, they have brown (thermogenic) fat to warm up after a dive, not white (thermo-insulating) fat to keep warm in the water like larger aquatic mammals & humans: an isolating SC fat layer would be much too heavy for such small mammals (Williams 1986, MacArthur 1986). Pinnipeds (which must be fast for catching prey & escaping predators) have body Tps like us or slightly higher, e.g. sea-elephants 36.5, fur-seals 37.5°C (Slijper 1958:359, McFarland cs 1979:774). But aquatic mammals that can afford to be slow often have lower body Tps, which saves energy, and allows longer dives. Hippos & many Cetacea have Tps of c 35.5°C, sea-cows probably even lower (Slijper 1958:359). Humans have an average body Tp like that of marine mammals, slightly lower than that of most terrestrial mammals. If ever we were savanna-adapted, we would have had much higher average body Tps.

On Wednesday, August 17, 2022 at 3:06:00 PM UTC-4, littor...@gmail.com wrote:
> Higher body Tps (esp. higher nerve & muscle Tps) allow faster reactions: for every 10°C, the velocity of the biochemical processes is more than doubled. Fast reactions are important for fighting rivals, catching prey, escaping predators, and in birds for flying. Generally speaking, the higher the nerve & muscle Tp, the better. But the costs of keeping body tissues at 40°C or more during the day are enormous. The energy expenditure of endotherms is several times that of ectotherms. Probably, Tps >40 or 41°C have other disadvantages: lipid solubility, protein denaturation, cell functioning etc. The highest known Tp in a living vertebrate is almost 48°C in the desert iguana. Desert birds have normal Tps between 39 & 42°C, and the domestic chicken can sustain a body Tp of 45°C for longer periods. Among mammals, the oryx can withstand a core Tp of 45°C, and Grant’s gazelle 46.5°C for many hours. But in humans, a rectal Tp of only 41°C may result in permanent brain damage (Chatton 1981:1,939).
> Most mammals that heavily rely on speed for survival (e.g. most middle-sized terrestrial mammals) have body Tps of at least 38°C, lower in the morning & after resting, higher in the evening & after exercise, e.g. horses 38°C, cattle & guinea-pigs 38.5, rabbits, sheep & cats 39, goats 39.5°C (Slijper 1958:359). Several small mammals that do not defend themselves by running away may have lower body Tps, e.g. hedgehogs, mole-rats, monotremes, pottos, sloths normally from 30 to 35°C, so they have much lower energetic expenditures than other mammals of the same diet. Small semi-aquatic mammals in temperate climates like minks or muskrats (weighing c 1 kg) have almost 40 & 38°C on land, but in the water the body Tp drops to <35°C after 20 minutes, so these mammals have to come on land every few minutes, they have brown (thermogenic) fat to warm up after a dive, not white (thermo-insulating) fat to keep warm in the water like larger aquatic mammals & humans: an isolating SC fat layer would be much too heavy for such small mammals (Williams 1986, MacArthur 1986). Pinnipeds (which must be fast for catching prey & escaping predators) have body Tps like us or slightly higher, e.g. sea-elephants 36.5, fur-seals 37.5°C (Slijper 1958:359, McFarland cs 1979:774). But aquatic mammals that can afford to be slow often have lower body Tps, which saves energy, and allows longer dives. Hippos & many Cetacea have Tps of c 35.5°C, sea-cows probably even lower (Slijper 1958:359). Humans have an average body Tp like that of marine mammals, slightly lower than that of most terrestrial mammals. If ever we were savanna-adapted, we would have had much higher average body Tps.
- Orangutans at rest have the 2nd lowest metabolism amongst arboreal mammals, after sloths. Both have long fur coat at adulthood, neither have much SC fat.

Op donderdag 18 augustus 2022 om 09:41:25 UTC+2 schreef DD'eDeN aka note/nickname/alas_my_loves:

> > Higher body Tps (esp. higher nerve & muscle Tps) allow faster reactions: for every 10°C, the velocity of the biochemical processes is more than doubled. Fast reactions are important for fighting rivals, catching prey, escaping predators, and in birds for flying. Generally speaking, the higher the nerve & muscle Tp, the better. But the costs of keeping body tissues at 40°C or more during the day are enormous. The energy expenditure of endotherms is several times that of ectotherms. Probably, Tps >40 or 41°C have other disadvantages: lipid solubility, protein denaturation, cell functioning etc. The highest known Tp in a living vertebrate is almost 48°C in the desert iguana. Desert birds have normal Tps between 39 & 42°C, and the domestic chicken can sustain a body Tp of 45°C for longer periods. Among mammals, the oryx can withstand a core Tp of 45°C, and Grant’s gazelle 46.5°C for many hours. But in humans, a rectal Tp of only 41°C may result in permanent brain damage (Chatton 1981:1,939).
> > Most mammals that heavily rely on speed for survival (e.g. most middle-sized terrestrial mammals) have body Tps of at least 38°C, lower in the morning & after resting, higher in the evening & after exercise, e.g. horses 38°C, cattle & guinea-pigs 38.5, rabbits, sheep & cats 39, goats 39.5°C (Slijper 1958:359). Several small mammals that do not defend themselves by running away may have lower body Tps, e.g. hedgehogs, mole-rats, monotremes, pottos, sloths normally from 30 to 35°C, so they have much lower energetic expenditures than other mammals of the same diet. Small semi-aquatic mammals in temperate climates like minks or muskrats (weighing c 1 kg) have almost 40 & 38°C on land, but in the water the body Tp drops to <35°C after 20 minutes, so these mammals have to come on land every few minutes, they have brown (thermogenic) fat to warm up after a dive, not white (thermo-insulating) fat to keep warm in the water like larger aquatic mammals & humans: an isolating SC fat layer would be much too heavy for such small mammals (Williams 1986, MacArthur 1986). Pinnipeds (which must be fast for catching prey & escaping predators) have body Tps like us or slightly higher, e.g. sea-elephants 36.5, fur-seals 37.5°C (Slijper 1958:359, McFarland cs 1979:774). But aquatic mammals that can afford to be slow often have lower body Tps, which saves energy, and allows longer dives.. Hippos & many Cetacea have Tps of c 35.5°C, sea-cows probably even lower (Slijper 1958:359). Humans have an average body Tp like that of marine mammals, slightly lower than that of most terrestrial mammals. If ever we were savanna-adapted, we would have had much higher average body Tps.

> Orangutans at rest have the 2nd lowest metabolism amongst arboreal mammals, after sloths. Both have long fur coat at adulthood, neither have much SC fat.

Yes, thanks, that confims our view.