Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site utah-gr.UUCP Path: utzoo!watmath!clyde!cbosgd!ihnp4!zehntel!tektronix!hplabs!hao!seismo!cmcl2!philabs!pwa-b!utah-gr!donn From: donn@utah-gr.UUCP (Donn Seeley) Newsgroups: net.misc,net.cooks,net.flame Subject: Re: Re: Truth in Advertising? (actually about skin shades) Message-ID: <1255@utah-gr.UUCP> Date: Sun, 25-Nov-84 17:49:53 EST Article-I.D.: utah-gr.1255 Posted: Sun Nov 25 17:49:53 1984 Date-Received: Thu, 29-Nov-84 05:40:10 EST References: <2804@ucbcad.UUCP> Organization: CS Dept., University of Utah Lines: 39 (None of this discussion has really been a good topic for net.cooks -- let's move it to net.misc or net.flame. Actually, net.flame has a nice ring to it when discussing properties of heat absorption and radiation...) From faustus@ucbcad.UUCP: What I've always wondered is why the closer to the equator people live, the darker their skin tends to be. It seems that in the interests of maintainting a reasonable body temperature, it should be just the opposite. Wayne Actually it's the skin shading of Caucasians that's more interesting. (My apologies to speakers of Kartvelian languages -- 'Caucasians' here refers to pale Europeans in general.) The skins of Caucasians darken upon exposure to sunlight, but this seems to mean that more radiation is absorbed, not less. This is often referred to as 'tanning', although for me 'tanning' your skin means peeling it off, immersing it in smelly and corrosive liquids, then nailing it to a wall. Isn't this darkening exactly the wrong way to go about maintaining body temperature? The 'body temperature' question is a 'red herring'; dark skin absorbs radiation in order to prevent it from penetrating into layers beneath the epidermis and causing damage (sunburn). 'White' skin is really transparent skin. People in sunnier climes are in more danger from radiation, so they tend to have darker skin. Of course skin shading also has a lot to do with where your ancestors came from, since populations don't change skin shade overnight... (Unless they're Caucasian chameleons!) It's always been amazing to me that the body's defense against radiation can be used to rationalize seating arrangements on a bus, or even more foolish things. Donn Seeley University of Utah CS Dept donn@utah-cs.arpa 40 46' 6"N 111 50' 34"W (801) 581-5668 decvax!utah-cs!donn