How to build a dinosaur

PUBLISHED : Sunday, 22 November, 2009, 12:00am
UPDATED : Sunday, 22 November, 2009, 12:00am

How to Build a Dinosaur
by Jack Horner and James Borman
Dutton, HK$208

What's the closest existing relative to a dinosaur? A giant lizard, perhaps? The answer, as this intriguing book by paleontologist Jack Horner points out, is a lot closer to home: it's a chicken. Birds, not reptiles, evolved from dinosaurs, and the chicken's bone structure has similarities to that of its giant forebears. Horner, one of the world's foremost dinosaur experts, aims to breed a miniature dinosaur from a chicken embryo so that it can be studied.

The idea may sound crazy, but it is actually good science.

Michael Crichton's novel Jurassic Park, later filmed by Steven Spielberg, began with scientists discovering dinosaur DNA in the blood of a fossilised mosquito that once fed on them. The DNA was then used to grow a dinosaur. That's a scientifically sound idea, says Horner, but the fossilisation process means it's unlikely dinosaur DNA will ever be found. Horner, who was the dinosaur adviser on Spielberg's film, has a different approach that doesn't use DNA. He works in the relatively new field of evolutionary developmental biology - sometimes called evo devo - an area complementary to DNA research.

Evo devo studies the process by which molecules grow to form body parts. To put it crudely, at some point in evolutionary history, dinosaur molecules started to grow into birds and not dinosaurs. If we can find what chemical messengers in the body initiated this change, we can stop the process happening in a chicken embryo and grow a dinosaur instead. We can, as Horner puts it, rewind the tape of evolution to the point where dinosaurs became birds and send it on a different path.

The secret of the change lies in the tail of the dinosaur. 'The dinosaurs had tails,' writes Horner in How to Build a Dinosaur: Extinction Doesn't Have to be Forever, 'some quite remarkable. Birds, now almost universally described by scientists as avian dinosaurs, do not have tails. They have tail feathers, but not an extended muscular tail complete with vertebrae and nerves ... how did this change occur? Is there a way to recreate the molecules involved in directing, or stopping, tail growth?'

He thinks that if the processes that occurred at the point the tail disappeared can be discovered, they could be halted in a chicken embryo. This would stop the evolutionary process and a dinosaur would grow instead of a chicken.

Horner is aware that his idea will sound crazy to those outside the scientific world, so the book is structured like a thesis. He spends a lot of time detailing the history of dinosaur research, from fieldwork finding fossils to DNA sequencing. He spells out advances in evo devo, and isn't afraid to cite scientists who disagree with some of the conclusions he's reached. He also includes a basic history of evolution to add context.

It is in the final part of the book that Horner talks in depth about his plan to turn back the evolutionary clock, and introduces the techniques that could be used. By this time, the reader has amassed so much knowledge about the field his project seems eminently reasonable.