In which I climb Mount Lewontin, not only without oxygen, but without clothes

I checked with two friends to ensure that one picture I’m posting today is not too salacious, and was assured that it was fine. It was taken in Salt Creek, near Death Valley, California, on January 12, 1981. The photographer was my colleague and friend Phil Ward, who went with me on a field trip to scout out sites for Drosophila work. (Phil is now a professor of entomology and ant expert at the University of California at Davis.)

January is a good time to collect flies, for the Death Valley region is the hottest place not just in the U.S., but in the world. But winter, especially January through early April, is cool and salubrious for the fly species I worked on: Drosophila pseudoobscura—a famous subject of evolutionary-genetic studies. This species, along with others, breeds in the dates grown in oases in the region, but almost certainly breed elsewhere as well, for you find them in profusion in areas where there are no dates (e.g., piñon pine/juniper forests). I spent several years part-time during my UCDavis postdoc trying to find where D. pseudoobscura breeds in the wild, and failed miserably. (I did find them breeding in garbage cans in urban areas.)

The work in Death Valley was a continuation of work started by my Ph.D. advisor, Dick Lewontin along with Steve Jones, a professor of genetics at University College London. At that time they wanted to see if protein variants (allozyme alleles) were “neutral”: that is, whether the variant forms of a gene that could be distinguished on an electrophoresis gel were equivalent in terms of natural selection. If they were “neutral” with respect to each other, then their frequencies would bounce around subject only to genetic drift: stochastic sampling of genes from one generation to the next. Natural selection could not tell them apart.

Dick and Steve thought that small oases like the Salt Creek Oasis, a few miles outside Death Valley National Monument (now Death Valley National Park), could serve as places to test whether allozyme variants were neutral, as they were thought to be self-contained and harbor resident populations of flies. (It turns out, though, that, due to the heat, Drosophila die out in summer and must repopulate from higher-altitude areas in winter.) If you could release thousands or millions of flies harboring different enzyme variants in different small oases, you might be able to go back repeatedly and see if the frequencies had changed. If they changed in all “replicate” oases in the same direction (i.e., variant 103 always rose to higher frequency at the expense of variant 104), you could conclude that the alleles were not selectively equivalent, and were differentially subject to natural selection.

These releases were done, and never came to anything. (I wouldn’t have done that experiment as natural selection is probably weak and the flies don’t go through more than a few generations before they die of heat in the oases.

However, visiting the area, I realized that one could do a different kind of experiment: release flies that were marked (fluorescent dust, used to make black-light posters, will mark flies nicely, as they clean it all off but leave a few grains on their thorax that can be seen under UV), and then determine if those marked flies could move across the desert. That is, if flies repopulate oases in the winter from cooler areas far away, surely they must be able to fly long distances. We wanted to see how far they could fly.

The picture below was taken when Phil and I were scouting Salt Creek Oasis for a release experiment of that type. (He was also collecting ants: a pismire fanatic, Phil’s never without his collecting equipment.)  The oasis looked propitious: it was a small clump of palms around a small spring, and there were flies there.  After deciding to do a migration study that March, we departed—but not before making our epic ascent of Mount Lewontin.

Mount Lewontin, not an official name but a monicker given by fly workers, is not a mountain at all: it’s a small rocky and dusty hill, probably about 150-200 feet high. As far as I know, though, nobody, at least among the fly workers, had ever climbed it. Since it was so low, one really didn’t need oxygen to ascend it. Rather than climb it without oxygen, then, I decided to climb it without clothes, wearing only my suede Stetson (reserved for field work) and my sneakers:

To those miscreants who think I’m making up all these semi-salacious tales (there was one on the last such post), this is proof that you’re wrong. (What, though, is that muscle in my upper thigh?)

Also, I gave Dick Lewontin an autographed copy of the photo after it was developed, and it hung on his office wall until he retired. Here it is with my faded handwriting clarified with a label:

“To my friend and teacher Dick Lewontin, who always climbed upward toward the naked truth.”

We came back in March and released about 100,000 flies, both D. melanogaster and D. pseudoobscura, that we’d captured the previous day in the big date grove at Furnace Creek Ranch in Death Valley, a famous tourist resort. We’d marked them, let them sit overnight in big buckets containing food so they could clean themselves from the fluorescent dust. And then the next evening, we gently lifted the lids to release the marked flies.

The next morning we collected at various places, including other oases, at various distances from the release site (we took great care not to carry any marked flies with us). The results surprised us: we collected marked flies, released in an oasis—a place where you’d think they’d stay—as far as 15 km from the release site the next morning (we caught 98 flies at two oases). They had either flown that distance or been blown by the wind.

These results, combined with those of other studies we did in Death Valley and in Maryland (see below), suggests that flies in or near an oasis occasionally “get lost”, and, when they’re just 20 or so yards from an oasis, cannot find their way back, and head out across the desert. Most of those die, but some make it to another salubrious place. This explains why flies are scattered not only throughout oases in the Death Valley region, but also can be trapped in godforsaken areas of the desert, including the Devil’s Golf Course, which has no vegetation at all! Here’s a picture of one of the places you can trap flies (we use baits of rotten bananas mixed with sugar, yeast, and some beer if we haven’t drunk it all):

The Devil’s Golf Course. Source: From Josh at California Through My Lens

Above are salt mounds: the remnants of an ancient sea (Lake Manly) that used to fill Death Valley. There is absolutely no vegetation: nothing for the flies to eat or breed on. And yet, they’re there. In fact, there’s almost nowhere you can go in this most desolate of deserts that you can’t trap flies. The desert is a thin sea of flies, most doomed but perhaps a few of them making it to another oasis, where they can yield what we call “gene flow.”

Here are the three papers we did on migration of Drosophila; the first is the Salt Creek Oasis release paper. I’m quite proud of these results but nobody ever cites them.

Coyne, J. A., I.A. Boussy, T. Prout, J.S. Jones, S. Bryant, and J. A. Moore.  1982.  Long-distance migration of Drosophila. Amer. Natur. 119:589-595.

Coyne, J. A., S.H. Bryant, and M. Turelli.  1987.  Long-distance migration of Drosophila.  2.  Presence in desolate sites and dispersal around a desert oasis.  Amer. Natur. 129:847-861.

Coyne, J. A. and B. Milstead.  1987.  Long-distance migration of Drosophila.  3. Dispersal of D. melanogaster alleles from a Maryland orchard.  Amer. Natur. 130:70-82.


  1. Teresa Carson
    Posted May 13, 2020 at 11:43 am | Permalink

    When you mentioned the Death Valley research in an earlier post, I was going to say that I thought that was where all the wild and crazy antics took place —— but that earlier photo looked rather serious. After all, it was taken with distinguished professors (all fully clothed). This looks more like the Death Valley trips I heard about. Good times.

  2. GBJames
    Posted May 13, 2020 at 11:45 am | Permalink

    It can’t be unseen!

  3. kathy mechling
    Posted May 13, 2020 at 11:46 am | Permalink

    Vastus lateralis is the contracted muscle on your right leg

    • Posted May 13, 2020 at 11:56 am | Permalink

      I was thinking gluteus medius. But just a guess really.

    • Ken Kukec
      Posted May 13, 2020 at 1:11 pm | Permalink

      Maybe that’s left over from all the time putting opponents in a leg lock as a school-boy wrestling champ in Deutschland.

    • Nicolaas Stempels
      Posted May 13, 2020 at 1:44 pm | Permalink

      It is the Tensor Fascia Latae, no doubt there.

      • kathy mechling
        Posted May 13, 2020 at 4:22 pm | Permalink

        Yes, TFL, not vastus. I was wrong. I didn’t look long enough.

    • rickflick
      Posted May 13, 2020 at 2:23 pm | Permalink

      Is that what the airport scanner thinks is a hidden, yellow, explosive?

    • Keith
      Posted May 13, 2020 at 3:47 pm | Permalink

      My muscle vote is for the tensor fascia lata. And what a fine specimen it is!

  4. rickflick
    Posted May 13, 2020 at 11:55 am | Permalink

    A remarkable place. Does this desert presage the temperate zone after global warming has had it’s way? The flies will have no refuge left. Neither will we.

  5. Posted May 13, 2020 at 11:58 am | Permalink

    You trapped flies at Devil’s Golf Course using buckets of rotten bananas, sugar, yeast, and beer? Time to reopen the file on spontaneous generation.

    • JezGrove
      Posted May 13, 2020 at 12:21 pm | Permalink

      Very good, Ron – thanks for the chuckle!

    • grasshopper
      Posted May 13, 2020 at 9:53 pm | Permalink

      Time flies like an arrow, fruit flies like a banana.

      • A C Harper
        Posted May 14, 2020 at 5:31 am | Permalink

        Time flies like an arrow, fruit flies like a banana, stage flies hide the scenery.

  6. Posted May 13, 2020 at 12:12 pm | Permalink

    I’ll add the detail that a copy of this photo was displayed in Dick Lewontin’s office, from the 1980s though at least the 2000s. My recollection is that it was inscribed by Jerry.

    • Posted May 13, 2020 at 1:10 pm | Permalink

      I’ve added the inscribed photo above.

    • davelenny
      Posted May 13, 2020 at 3:52 pm | Permalink

      This is proof that you’re wrong.

      Butt is it rock-solid proof? On my iPad screen, the hat suggests this is Indiana’s brother, Indecent Jones.

  7. Simon Hayward
    Posted May 13, 2020 at 12:22 pm | Permalink

    Clothing optional graduate studies, followed by clothing optional postdoc, OK. Did you start dressing on a regular basis after getting a faculty position? I’m imagining a tenure committee discussing the antics of a naked Assistant Professor. It doesn’t seem like a promising start to the meeting 🙂

    Amazed you found drosophila at the devils golf course. Last time I was there it was hotter than hades.

    • eric
      Posted May 13, 2020 at 12:54 pm | Permalink

      I thought the same thing at first. But let’s remember PCC is selecting a couple (so far!) of the most memorable incidents out of his late 20s. I’d bet 2 nudities per someone’s 20s isn’t at all unusual. Looking back on my own 20s, I can remember two myself, and I was probably a lot more socially conservative than that long haired anti-war hippie (admiration intended) you see in the pic!

      • darrelle
        Posted May 13, 2020 at 1:43 pm | Permalink


        I once streaked across the lawn at the Polynesian resort in Disney World.

    • Posted May 13, 2020 at 1:18 pm | Permalink

      It’s not hot in Jan-March!

      • John Conoboy
        Posted May 13, 2020 at 1:49 pm | Permalink

        My wife and I camped in Death Valley in December 1967 and it was a lovely temperature. Did not see any drosophila but we did find a scorpion (species unkown) in our bedding as we were breaking camp. Several years ago we drove past Death Valley in the summer and it was 124 degrees F. there. Did not have time to go into the park though. We camped again at Furnace Creek a few years ago in December and it was below freezing at night.

  8. JezGrove
    Posted May 13, 2020 at 12:41 pm | Permalink

    Thanks to the Stetson and PCC(E)’s Jewish heritage, now I’ve got “Down the Dustpipe” on my brain – though no jeans, $10 bill, and a long way from New Orleans. Guess we better make it the version on this album:

  9. darrelle
    Posted May 13, 2020 at 1:44 pm | Permalink

    Definitely some muscle showing there Jerry. Looking very fit.

  10. Posted May 13, 2020 at 2:15 pm | Permalink

    Since many parts of the floor of Death Valley are below sea level, I wonder whether the peak of Mount Lewontin is also below sea level. Not to detract from your famous work on speciation, but the Death Valley fly work by you and your coworkers is classic.

    A colleague of mine in my department attended the University of Rochester in the 1960s and had a memorable genetics class from Dick Lewontin. Later she and her husband were hiking in Death Valley and were about to set up camp for the night when they saw a campfire nearby and thought that they might join them. So they went over and said hello. It turned out to be Dick Lewontin and Tim Prout.

    • steve jones
      Posted May 14, 2020 at 2:38 am | Permalink

      Joe – good to see you; yes, they were happy times. I just write books nowadays.


  11. Posted May 13, 2020 at 2:27 pm | Permalink

    Jerry’s post is a Death Valley coincidence for me – just watched Darwin on Amazon. A decade old, but curiously interesting.

  12. Steve Pollard
    Posted May 13, 2020 at 3:21 pm | Permalink

    Another chapter for the PCC(E)) memoir that we’re all hoping will hit the streets one of these days.

    Jerry wrote: ‘we use baits of rotten banana…’ The present tense! I guess you’re still there, doing it, in spirit at least.

    • phoffman56
      Posted May 13, 2020 at 3:45 pm | Permalink

      Bjorn Daehli (sp?) claimed that rotten bananas were better for your health. One cannot argue against 15 Olympic golds, or whatever it was. Maybe swallowing a few flies at least adds to the protein.

  13. phoffman56
    Posted May 13, 2020 at 3:42 pm | Permalink

    Was there a pic of you on the summit? Surely that one would be full frontal for full effect.

    “I wonder whether the peak of Mount Lewontin is also below sea level. ”

    Need anti-oxygen then, not O_2, but O_-2.
    Or maybe a tank of CO_2 to breathe for dilution purposes.

    Above is jokes, but too much oxygen makes a person dizzy, does it not?

    • Phil Ward
      Posted May 13, 2020 at 5:08 pm | Permalink

      Consulting Google Earth I find that Mount Lewontin, magnificent hillock that it is, reaches a giddy height of 213 meters above sea level. The base is at an elevation of ~150 m. This takes nothing away from Jerry’s remarkable, unassisted ascent.

      • phoffman56
        Posted May 13, 2020 at 6:33 pm | Permalink

        Well, if there are no pitons to help me, I ain’t goin’.

        Anyway, 213 + 150 = 363 > 1,000 feet is a good jaunt. I live 60 feet above a river, and the idea of up-and-down about 17 times is not appealing, at least by retirement age.

  14. daniaq
    Posted May 13, 2020 at 6:12 pm | Permalink

    Hahaha! Great!

  15. uommibatto
    Posted May 13, 2020 at 7:04 pm | Permalink

    Very interesting account of field work for someone (me) who is not in this field at all, thanks.

  16. grasshopper
    Posted May 13, 2020 at 9:59 pm | Permalink

    I am curious in regard to the number of flies released. How was the total number estimated? Was the number of flies trapped in one jar, after X hours, multiplied by the total number of jars.

    • Posted May 14, 2020 at 3:59 am | Permalink

      I believe we took a sample but I can’t recall. At any rate, the conclusion, that flies can fly long distances in a short time, doesn’t rest on the number released.

  17. ubernez
    Posted May 13, 2020 at 10:06 pm | Permalink

    But, he has no fly in this photo…

  18. Matt
    Posted May 13, 2020 at 10:57 pm | Permalink

    And you decided to climb naked because?

    • Saul Sorrell-Till
      Posted May 15, 2020 at 5:54 am | Permalink

      if you looked like that, wouldn’t you?

  19. Jonathan Wallace
    Posted May 14, 2020 at 8:41 am | Permalink

    I hope you didn’t slip during the ascent or subsequent descent – those rocks look pretty abrasive!

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