Seeking symmetry on a sunday morning (updated)

I spent last Sunday hiking with friends in the Shawangunk Ridge, in New York state. The Gunks, as it is locally known, is a ridge of bedrock that extends from the northernmost tip of New Jersey to the Catskill Mountains in New York. It was an incredibly foggy day, so we didn’t get to see any of the scenic vistas. But we did get to enjoy the weirdly diverse vegetation, all of which was covered in dew. The highlights were hiking through a beautiful ice cave, and having lunch on a ledge overlooking a 180 feet (54.6 m) tall waterfall. That’s a few feet higher than the vertical drop of Niagara falls. Check out some of my pictures below (fullscreen for full effect).

In the last image, you can use the people as a scale to get a sense of the size of this waterfall. The vertical cliff face that you see was once the site of a geological fault, where a crack formed in the bedrock and broke the symmetry. Rock on one side of the fault then slipped under, as rock on the other side got pushed above. Erosion has since gotten rid of the topsoil at this fault line, exposing the layers of bedrock beneath. It’s a striking testament to the power of geological forces.

The layers of rock that you see have been dated to about 430 million years ago. This was an interesting time in our history. It is when our ocean-dwelling fish ancestors started incorporating a new invention into their bodies – bone. It was also the time when these ancestors (who would later give rise to amphibians, reptiles, birds and mammals) parted ways with the ancestors of some rather interesting characters. These were the Coelacanth and the Lungfish, the so-called ‘living fossils’ of the ocean.

Meet the Coelacanth. One of our more interesting relatives

Of course, there’s really no such thing as a living fossil, as Darwin was well aware when he coined this phrase. Every species alive today has been evolving for just as long as we have (and usually much longer, because evolution is measured in generations and not years). But the Coelacanth, and to a lesser extent the Lungfish, are the few cases where this phrase is appropriate. Fossil records and genetic comparisons bear out that Coelacanths have indeed not changed a whole lot for hundreds of millions of years. Our ancestors from this time may, at least superficially, have looked something like this.

Continue reading Seeking symmetry on a sunday morning (updated)

Why moths lost their spots, and cats don’t like milk. Tales of evolution in our time.

In the children’s game of hide-and-seek, it doesn’t matter much whether you win or lose. In the animal kingdom, however, the stakes are significantly higher. If you’re found, you’re food.

And death is not just the end of the individual, it’s the end of a lineage. Organisms that die before they can reproduce deny their genes a road to the next generation. In this simple fact lies the engine of change. For example, genes that make a prey more camouflaged will end up increasing their reproductive success, whereas genes that make them more noticeable are not going to get very far. In this way, natural selection is driving prey to become better hiders, and predators to become better seekers.

Nowhere is this evolutionary race more evident than in the case of the peppered moth. This is a species of moth that is found all across England and Ireland. When people first studied them in the early 1800s, almost all the moths looked something like this:

As you can see (if you’re looking closely), the white and black speckles are effective camouflage. For ages, these moths have hidden on light colored trees and lichens. Over time, they have evolved this distinctive pattern to help them evade the notice of the birds that prey on them.

But just fifty years later, things were beginning to change. By the 1850s, moths of the same species had stumbled upon a new color. These new moths were called carbonaria after their carbon-black color, to distinguish them from their salt-and-pepper colored relatives with the dull name typica.

By the end of the nineteenth century, the change was drastic. In 1895, a study in Manchester showed that 95% of the peppered moths were now of the black type. So what was going here? What could cause such an incredible change in appearance in just a hundred years?

Continue reading Why moths lost their spots, and cats don’t like milk. Tales of evolution in our time.

Destroying the disposers of death: will India rescue its few remaining vultures?

Indians today can hardly recall the last time that they saw a vulture. In the 1990s, these majestic birds were a common sight in the subcontinent, and would show up wherever there was exposed carrion. As a child, I remember marveling at vultures circling at impressive heights, probably looking back down at me with their incredible eyesight, their wings outstretched as they effortlessly hovered on columns of warm air.

But since the nineties, their numbers have been falling dramatically in India, Pakistan and Nepal. The scale is astonishing – for every thousand white-rumped vultures in 1990, only one is alive today. A similarly sad story holds for the Indian vulture and the slender-billed vulture. Together, all three Asian vultures are now listed as being critically endangered.

The White rumped vulture, Gyps bengalensis

So what’s going on? It’s not that they are being hunted. For one thing, the killing of all wild animals in banned in India. But also, vultures have always provided a much valued ecological service. Most villagers dispose of dead animals by dumping the carrion. And they rely on the vultures to clean up.

Vultures have an undeservedly bad reputation. Because we associate carrion with disease, people believed that vultures spread diseases. But in fact, we now know that the opposite is true. Their powerfully corrosive stomach acids allow them to safely digest carrion that would be lethal to other scavengers, wiping out bacteria that can cause diseases like botulism and anthrax. They are the purgers of death and disease.

In their absence, populations of feral dogs have exploded, bringing with them the threat of rabies and human attacks. And if rats follow suit, India would face a new public health nightmare as it tries to control the spread of rodent-borne diseases like bubonic plague [1].

Continue reading Destroying the disposers of death: will India rescue its few remaining vultures?