Bactrian camels in Ladakh

First shock: Bactrian camels (Camelus bactrianus) survive entirely as domestic animals, or in populations which have gone feral. Wild Bactrian camels are a separate species, found in extremely small numbers across northern Asia. Second shock: Asian camelids diverged from the new world camelids only about 25 million years ago! Did founder populations walk across land bridges during the ice ages? Third shock: the two-humped Bactrian camels and our familiar one-humped Dromedary diverged less than 800,000 years ago. As a result they can still interbreed and produce fertile offspring. In a thought-provoking book called Otherlands, Thomas Halliday discusses exactly this process of speciation. He draws an analogy to a river which bifurcates into two streams, and asks at which point one can begin to say that a parcel of water belongs to one stream or the other. Near the beginning of the bifurcation it is not clear at all; a little parcel may flow towards one stream before an eddy sends if off in another direction. Similarly, as two species begin to diverge, two individuals of opposite sex from the two species will still produce an offspring. Only later, when the species have diverged fully, will they not be able to produce fertile offspring. Dromedaries and Bactrian camels seem to be at this stage.

But all this was background. I was trying to figure out why there are Bactrian camels in Ladakh. As with many Ladakhi puzzles, the answer is the Silk Route. It passed Leh, crossed Khardung La, traveled across the Valley of Death, now called the Shyok river valley, funneled north into Tajikistan, before bifurcating into two: the southern route went to Kabul and Peshawar, the northern to Samarkand and on. Tajikistan is at the eastern border of the ancient Persian province of Bactria, and it supplied camels to cross the high deserts of Ladakh and Tibet. When modern borders snapped into place in the 1950s, a small population of Bactrian camels were left in the Nubra valley. In this century they are being bred again to provide safaris for tourists. The Family walked among them in Hunder, where the largest herds are, and came back with these photos.

Familiars

Many years ago when The Family wanted to start birding, we discovered that the ship-breaking yard in Sewri was a place where we could watch water birds. We went there every weekend for several months and became familiar with the common sandpiper (Actitis hypoleucos). Because of its name, I thought it wasn’t of much interest. Later I realized that the name merely refers to how easy it is to spot. And only now I realize that it is a very special species. But before I tell you why, let me just say that when you start watching birds you accumulate many photos of the more common ones, and eventually you begin to see their special beauty. I’m very fond of the featured photo of the common sandpiper which I took in a patch of waste water runoff behind Chhapar village in Rajasthan. I’m equally happy with the photo below of the common redshank (Tringa totanus), another sandpiper, taken in the same place. The redshank’s piping call tells you immediately why the family is called sandpiper. These beautiful waders can be seen across Africa, Asia, Europe, and also in parts of Australia.

Across the American continents one sees the spotted sandpiper (Actitis macularius), very closely related to the common sandpiper. So closely related that there is still gene flow between these two species; hybrid lineages have been spotted now and then. It seems that the species split very recently in geological time. Usually when we look at two different species, say a tiger and a leopard, they are not able to produce viable hybrids. However, when you trace them back to their common ancestral population, the distinction becomes less clear. There is a point at which the ancestors of the leopards and of the tigers could not be distinguished at all. A little later they would have been distinct, but still able to interbreed. Only with the passing of time have they come to be as distinct as they are today. The two species of Actitis remind us that the split between species occurs gradually. It amazes me to see this creative act of evolution frozen in time.

The battle of the sexes

You can tell that I’m a pretty amateurish birdwatcher because I can’t yet look at a bird in passing and ask “Which wheatear was that?” I have to look carefully at birds like this before I can say that it is a desert wheatear (Oenanthe deserti). Then I have to look carefully again and again at the quite differently coloured bird below, and ask The Family “Is that a female of the desert wheatear?” That’s why I’m quite in awe of the great field ornithologists like Salim Ali and Evigeniy Panov who could reputedly identify birds that flew across the periphery of their vision.

Entirely through behaviour and ecology, Panov argued that the blackstarts (genus Cercomela) and wheatears (genus Oenanthe) are related. Along broad lines his hypothesis was proven correct by molecular methods, although he continues to dispute the details. Genetic studies depend a lot on which genes are sampled, and a true picture emerges only when many genes are studied together, and Panov may perhaps yet turn out to be correct even in some of the smaller details. In any case, his observations seem to be driving much of the more recent work on the evolution of chats and wheatears.

The female is hard to spot. Panov tells us why this should be expected. Desert wheatears are opportunistic nesters. They nest in the mouths of holes dug by rats and Jirds when possible, in any other cover which is available, and even in open ground if no cover can be found. The female incubates the egg entirely without help from the male. Since this can be entirely exposed, it is useful to have colours which help her to fade into the background. Even in the photo above, she does not stand out. Before you mentally label the father as an useless pig, remember that mammalian mothers have to incubate their fertilized eggs with absolutely no help from fathers. At least some species among our theropod dinosaur cousins, the birds, have distributed the job better. I’ve learnt one trick from Panov for distinguishing it from the female of the Isabelline wheatear: look for a rapidly wagging tail with changes in rhythm.

Umami and starch

On such a full sea are we now afloat,
And we must take the current when it serves,
Or lose our ventures

William Shakespeare (Julius Caesar, Act IV, Scene 2)

Swells which ride on a tide never quite drain away. That seems to be the fate of the second wave of epidemic around us. Still, we brave the rip tide a couple of times a week: once by going out to eat, then again by meeting friends and family, one couple on one. On our last two outings we ordered, among other things, sausages and bread. Once it was Lebanese sausages with its flat bread (featured photo), the second time it was a Goan sausage with pao (below). These are wonderful, satisfying tastes. First the kick of the starch, then the garnish with its salts and sours and chili, and finally the long finish of the umami. If you are a meat eater, you know the satisfaction of well cooked starch and meat.

It led me to wonder about the universe of flavours that we build daily in our kitchens. Some searching led me to a well-written review of the current state of our knowledge about tastes. The first thing that surprised me is that taste and the perception of flavour are different. In fact, there are taste receptors in our stomach and intestines which order our bodies to metabolize food, but they don’t add to our perception of flavour. But the major surprise was how tightly the sensation of taste is connected to survival. It is not a complete surprise of course, because it is fairly common knowledge that many plant toxins are extremely bitter in taste, and we tend to avoid sharply bitter food. What is less widely known is that bitterness can involve pre-emptive nausea to remove the toxin from our stomach. The increased sensitivity to mild bitterness is said to trigger nausea during the first trimester of pregnancy when the major organs of the fetus begin to develop. It is also the identical response which we seek to suppress when we advise people not to drink on an empty stomach.

The ability to taste umami seems to have evolved in the pre-human lineage as they diverged away from our nearest living relatives and started foraging in grasslands, and decreased their reliance on fruits. Unlike us, chimpanzees cannot taste this component of our food. The umami taste appears as proteins denature slightly, either by rotting or cooking. We can tell when proteins in food reach the state when our stomachs and the pro-biotic bacteria inside us can begin to digest them by the glutamates and ribonucleotides that are sensed by the umami taste buds in our mouths. Fresh meat does not have an umami taste, so carnivores do not have these receptors. Sea-lions have evolved very far from other mammals by losing all sensation of taste, since they use their visual senses to identify prey and then swallow it whole. Perhaps only the dinosaur ancestors of birds had as finely developed developed a taste for umami flavours as us.

Our liking for starchy food is more subtle. I could not think of a specific taste of starch, but I love it when I eat it. Many animals can digest starch through enzymes produced in the pancreas. In us, and strangely, also in rats, this is supplemented by the production of the same enzyme in our tongues. This breaks down starches very rapidly in our mouths, so that we have no difficulty in swallowing dry toast or thick porridge. There are taste receptors on our tongue that sense both this enzyme and the malty predecessors of glucose (called by mouthfuls of names such as malto-oligosaccharides) that it produces by pre-digesting starch in the mouth. These receptors connect to parts of the brain which process taste without actually being identified as a distinct taste. I suspect that large scale addition of starch to our diets has been so recent, on the evolutionary scale of time, that our brains have not evolved to consciously processing these sensations as a separate taste.

Our brains may not have begun to process starch as a separate taste, but already our bodies have begun to evolve to identify these tastes. Some of us have more amylase receptors on our tongues. Such individuals seem to trigger production of insulin even before the starch reaches the stomach, and thereby lower the glycemic response to the food. Could the observation that diabetes runs in families similarly signal individuals who have heritably lower levels of these receptors? How did rats evolve this sense? Did they have it before they became ancient household pests, or did human agriculture and storage stimulate this evolution in rats? A tasty lunch seems to be a lesson about evolution in action.

Hot earth

After reading about mudskippers yesterday, I eventually connected them with a bit of information I’d forgotten. In the time that mangrove forests and mudskippers were beginning to evolve on the western shores of the Tethys Ocean 50 million years ago, the earth went through a climate catastrophe. Geological eras have names that I find fascinating. This was the beginning of the Eocene epoch, the name means the dawn of modern times. If you want to be more specific, you might call it the Ypresian age, a 8 million year blink of time starting 56 million years ago. What I remembered was that in the Ypresian age the earth went through a heating event that we call the Paleocene-Eocene Thermal maximum (PETM). Temperatures across the earth were between 5 and 8 degress Celsius higher than it is today.

At this time the continents had not yet reached where they are today, as you can see in the map above, but they are not completely unrecognizable. The deep oceans saw a tremendous extinction; between a third and a half of ocean species died out. The oceans became acidified and hot. Their levels rose, water saturated the air. The poles warmed more than the rest of the world. As a result, the Antartic was forested and ice free, and tropical rain forests covered southern Germany. Canada, as far north as what is today Baffin Bay, had swampy conifer forests regularly ravaged by forest fires. The part of India which is now the Thar desert seemed to have had extreme rains and weathering during that time, whereas northern Spain was a parched desert. It is hard to prevent a large body from heating up, so mammals became smaller. This may have had many consequences, but one that has been followed up is that it encouraged a rapid evolution in the ancestors of today’s horses.

Small boat in Bhitarkanika National Park, Odisha

Although the map of this world looks almost the same as ours, this hot and rain-drenched world is not suited for agriculture. Estimates of our carbon future showed that in “business as usual” scenario we will be there by the end of the century: in the time of the grandchildren of the millennials. There is a reason that projections stop at the year 2100: no climate simulation remained believable beyond that. Very recently though, a climate model was able to reproduce the PETM using reliable estimates of the amount of CO2 then present in the atmosphere, by following the small-scale dynamics of clouds more accurately. This simulation seems to say that the future temperature rise could be more extreme than had been predicted. We live in unsettled times.