Where I live it’s quite temperate most of the year, if not sweltering, and this counts a subtropical region. Right in the depths of January and February, though, there are weeklong stretches where it’s really intolerable to be outside without a coat (as I was reminded today); it’s nowhere near freezing, but the high humidity makes it really clammy, and even a light rain would probably do me in from exposure in short order. So I don’t think people could live here if they always went absolute starkers and didn’t have a hut to hide in, and the human race would be firmly confined to the tropics, even more so than other great apes that have the benefit of fur. Or people hardier than I think, or would they retain or develop fur Lamarck style, giving them a broader geographical range?
I am afraid you are just being a wimpy modern person. 
The Tasmanians went entirely without clothes and it is much colder than your climate. The people of Tierra del Fuego did as well. That is on the southern tip of South America, not so far from Antarctica. Tierra del Fuego - Wikipedia
Wikipedia’s information about the adaptations to cold climate for the Yaghan people of Tierra del Fuego is quite interesting:
Where in the world would humans ever be, without shelter and fire? We’ve had both since before we were modern humans. In fact, it’s been argued that fire is one of the things that made us Homo sapiens
So they were actually able to have their kayak and heat it! :eek:
shoves njtt out in the cold
If I could amend the OP, I think I should have excluded fire as well. I was curious about purely physiological constraints, absent even the most basic cave man technologies. Basically, in what environments can we survive as apes, and apes alone?
One book I had many years ago suggested the Tierran del Fuegans (?) would have animal hide robes. They could wear them like blankets - but nothing actually shaped and tied like normal clothing, and of course they would shed their “blankets” when they needed to chase game or do anything else active.
Nice 
No, it’s horrible. If there were a god or any kind of justice under the skies, **njtt **would be banned with extreme prejudice for that horrible, horrible pun. Horrible pun!
The first humans known outside Africa are *Homo erectus/H. georgicus * from Dmanisi in Georgia in the Caucasus, which date to about 1.8 million years ago. This is well before the earliest (disputed) evidence for the controlled use of fire about 1 million years ago. So we can assume these individuals were living in a temperate area without fire.
Nearby Tbilisi today gets down to about 29 F in January, and can get down to -12 F. While the climate could have been different 1.8 million years ago, this was the beginning of the Pleistocene and so probably wasn’t that much warmer if at all.
Homo erectus lived through much of temperate Europe and Asia, as far north as Beijing and similar latitudes to about 40 degrees North, over a long period before acquiring fire. There is also no evidence that they used clothing. Now, H. erectus weren’t modern humans but I think we can conclude that living in temperate regions without fire and clothing is not beyond basic human physiological capacity. However, surviving in areas where the temperature went below freezing for a significant period of time would probably require the availability of some kind of natural shelter.
While it would be fair to exclude fire and clothing, making artificial shelters should probably be allowed since both chimps and gorillas sleep in nests they make at night.
Would Homo Erectus have been hairier than modern humans? Also, were the Tierra Fuegans hairier than the typical modern human? It seems not unpossible, we all have hair, it’s just mostly very fine; I wouldn’t think it would take long to select for humans with coarser, longer body hair.
Not noticeably.
We don’t really know, and it certainly would be possible. But I don’t know that even ape-type hair would give that much protection without a furry undercoat.
It’s actually colder in other parts of Australia, such as where I am in Canberra (last winter’s minimum averaged just below freezing, with lots of -3 and -4s)
Whether or not locals gave protective clothing a shot I cannot say.
Key to naked human hardiness is not hair but brown fat, metabolically active tissue that is present in newborns and further develops in children regularly exposed to low temperatures. Any Fuegian, Tasmanian, Homo erectian etc. would have loads of brown fat in their system compared to us postmodern humans, and would function better in the cold, as brown fat delays the onset of the inefficient shivering reaction. Further, studies among the Inuit have shown that they have more active circulation in the extremities, as illustrated by bare-handed Inuit doing everyday chores in extremely cold weather. Fine motor skills is something we lose first when hypothermia sets in, and losing it may be lethal in a survival situation, where the ability to use tools, manipulate kindling, tie knots etc. is critical.
Among peoples with traditionally minimal clothing, very low nighttime temperatures have been recorded within the sleeping quarters of Australian Aborigine and South African San campsites, and the abnormally high rest metabolism of the inhabitants documented. Many inconspicuous developments are at work here, mainly due to a lifetime of sub-lethal but systemically challenging exposure.
I wonder if, without fire, modern humans wouldn’t be constrained more by food supplies than by temperature. Our brains need a lot of fuel. Our wimpy little jaws can’t deal very well with raw non-domesticated food, and even what we can eat, we get much less energy from raw food than from cooked food. A fire-less human is going to have a giant challenge just getting enough calories, in most environments.