Unit 5. Domesticated animals

Script 9. Canine evolution

The company of wolves

Man’s best friend originated in Europe, not East Asia.

Foxes can be tamed deliberately, by selective breeding. But this probably recapitulates a process that happened accidentally, many millennia ago, to wolves. The product of that was the animal now known as the dog. But where on Earth this happened is moot. Fossils have been used to make the claim for places as diverse as Russia and the Middle East. Genetic evidence has pointed towards East Asia, with some people believing that New Guinea singing dogs and their Australian offshoots, dingoes, are largely unchanged descendants of the first pooches. Olaf Thalmann of the University of Turku, in Finland, Robert Wayne of the University of California, Los Angeles, and their colleagues beg to differ. They think Fido was born in Europe, and that they have the DNA to prove it.

The DNA in question is from mitochondria: cellular power packs that have their own genes. Because each cell has lots of mitochondria, but only one nucleus, there is a better chance of getting mitochondrial genes than nuclear genes from a fossil. And that, as they describe in Science, is what Dr Thalmann, Dr Wayne and the rest of the team did.

They extracted mitochondrial DNA from 18 fossil canids, making sure to include the earliest doglike creatures that show skeletal signs of domestication. (These date from 36,000-15,000 years ago.) They then compared what they found with DNA from 49 modern wolves collected from all over the northern hemisphere, and also with that from 77 modern dogs.

Modern dogs, they knew from previous studies and confirmed with this one, belong to four genetic groups different branches of the canine family tree, in other words. Several fossil canids from Europe, the researchers found, also belong to one or other of these groups, as do the continent’s modern wolves. Middle Eastern and Asian wolves, both ancient and modern, are, by contrast, not members of any of these groups and cannot therefore be closely related to modern dogs.

Three dog fossils from the Americas, dating back between 1,000 and 8,500 years, also shared their ancestry with modern mutts. Presumably their forebears accompanied the first American colonists 15,000 years ago when they crossed the Bering land bridge that linked the New and Old Worlds before the sea level rose to flood it at the end of the last ice age.

Dogs’ division into four groups means one of two things. Either domestication happened more than once, or each group is descended from post-domestication crosses between dogs and wolves that brought new mitochondrial DNA into the line. Regardless of which is true, this study seems both to pinpoint where dogs come from and to confirm that their domestication predates the invention of agriculture, about 10,000 years ago.

For reasons yet unknown, wolves and humans first got together when people still hunted and gathered for a living. Perhaps their similar ways of life both species then dwelling in small, mobile bands allowed the two to collaborate in hunting or defence. Or perhaps they just enjoyed each other’s company. Rather like today, in other words. (From The Economist, November 16, 2013)

Script 10. Fish farming

High-tech breeders

You do not have to use genetic engineering to benefit from genetics.

The Japanese are great guzzlers of fish, but fish are in finite supply. And farming them to increase that supply can be tricky, because many species are susceptible to disease when crowded together. That fact is the impetus behind a study led by Takashi Sakamoto of the Tokyo University of Marine Science and Technology. Dr Sakamoto is using a combination of modern genetic techniques and classical breeding to produce fish that can survive crowding without falling ill.

His first task was to establish genetic maps for each of the species involved - flounders, trout and amberjack. Such a map is not a complete DNA sequence, which would be unnecessarily detailed, but rather a set of signposts, using which a geneticist can navigate his way around an animal's chromosomes. The signposts are places where DNA routinely differs within a species from one individual to another, and does so in characteristic ways. When sperm and eggs form, blocks of DNA from a creature's mother and father are swapped around, taking the signposts with them. If you have enough signposts it is possible to follow these blocks through the generations.

Dr Sakamoto now has genetic maps for hundreds of individual fish, and he also has data, collected in collaboration with Japan's three main fishery-research institutes, on how well these fish did when faced with plague or pestilence. He has thus been able to tease out which versions of which signposts are associated with rude health.

It is not the signposts themselves which confer protection from disease. That is done by nearby genes. However, gene and signpost travel together from parent to offspring, so the presence of the one can be inferred from the presence of the other. And that gives Dr Sakamoto an invaluable head-start when it comes to breeding disease-resistant fish. He is able to see how many resistance genes have ended up in each animal and then pick the most resistant to breed from. He thus gains much of the advantage that might come from actual genetic engineering (ie, directly transplanting resistance genes into fish eggs) without having to do the engineering itself.

It also means he can breed healthier fish without necessarily knowing what the health-giving genes are - though it would obviously be a bonus to have such knowledge, and he is indeed busy searching the DNA near the relevant signposts to find the truth.

Dr Sakamoto's research group has already managed to produce flounders which are resistant to viral lymphocystis (a serious problem on flounder farms) and these are now in the shops. It has also produced trout that are immune to a bacterial infection called cold-water disease, and it is now working on amberjack that will be less likely to suffer infestations of monogean, a parasitic flatworm. The upshot should be healthier, cheaper fish - and happier fish farmers. (From The Economist, November 3, 2012)

Script 11. Animal rights

Whales are people, too

A declaration of the rights of cetaceans.

The "Declaration of the Rights of Man" was a crucial step in the French revolution. The document, drafted by the Marquis de Lafayette, marked a break with the political past by proposing that everyone, however humble his birth, had certain inalienable civil rights. These were liberty, property, security and resistance to oppression. Merely being a man conferred them.

These days, such rights extend to women as well. But what if you are not human? A session on cetaceans at the AAAS meeting discussed a proposal that whales and dolphins, too, should have rights. The suggestion of the speakers was that the protections these species are afforded by human laws should be extended and recognized not as an indulgence of the human aristocracy towards the bestial peasantry, but as a right as natural as those which humans now afford, in the more civilised parts of the world, to themselves.

The proposition that whales have rights is founded on the idea that they have a high degree of intelligence, and also have self-awareness of the sort that humans do. That is a controversial suggestion, but there is evidence to support it. Lori Marino of Emory University, in Atlanta, Georgia, reviewed this evidence.

One pertinent observation is that dolphins, whales and their kind have brains as anatomically complex as those of humans, and that these brains contain a particular type of nerve cell, known as a spindle cell, that in humans is associated with higher cognitive functions such as abstract reasoning. Cetacean brains are also, scaled appropriately for body size, almost as big as those of humans and significantly bigger than those of great apes, which are usually thought of as humanity's closest intellectual cousins.

Whales and dolphins have complex cultures, too, which vary from group to group within a species. The way they hunt, the repertoire of vocal signals and even their use of tools differs from pod to pod. They also seem to have an awareness of themselves as individuals. At least some can, for example, recognise themselves in a mirror - a trick that humans, great apes and elephants can manage, but most other species cannot.

Thomas White, of Loyola Marymount University, in Los Angeles, then discussed the ethical implications of what Dr Marino had said. Dr White is a philosopher, and he sought to establish the idea that a person need not be human. In philosophy, he told the meeting, a person is a being with special characteristics who deserves special treatment as a result of those characteristics. In principle, other species can qualify. For the reasons outlined by Dr Marino, he claimed, cetaceans do indeed count as persons and therefore have moral rights - though ones appropriate to their species, which may therefore differ from those that would be accorded a human (for example, the right not to be removed from their natural environment).

Chris Butler-Stroud, of the Whale and Dolphin Conservation Society, in Britain, and Kari Koski of the Whale Museum in San Juan Island, Washington state, then charted some of the hesitant steps already being taken in the direction of establishing cetacean rights. Mr Butler-Stroud showed how the language used by international bodies concerned with these animals is changing. The term "stocks", for example, with its implication that whales and dolphins are a resource suitable for exploitation, is being overtaken by "populations", a word that is also applied to people.

Ms Koski gave an even more intriguing example. She told of how a group of killer whales that lives near Vancouver, passing between waters controlled (from a human point of view) by Canada and the United States, have acquired legal protection even though the species as a whole is not endangered. After a battle in the American courts these particular whales have been defined by their culture, and that culture is deemed endangered.

The idea of rights for whales is certainly a provocative one, and is reminiscent of the Australian philosopher Peter Singer's proposal that human rights be extended to the great apes - chimpanzees, bonobos, gorillas and orangutans. Like Dr Singer's suggestion, though, it does ignore one nagging technicality. The full title of the French revolutionary document was "Declaration of the Rights of Man and Citizen". No one has yet argued for votes for whales and dolphins. But considering some of the politicians who manage to get themselves chosen by human electorates, maybe it would not be such a bad idea. (From The Economist, February 25, 2012)