08.05.08

Alife: the experimental falsification of Darwinian natural selection

Posted in Evolution at 3:39 pm by nemo

Can we make software that comes to life?
This article tells it as it is: none of these ‘artificial life’ programs can deliver that they promise. And yet the point doesn’t sink in, it seems.
Let’s be clear: this is an issue of randomness, and thence natural selection. A naturalistic process that is not chance might well be able to do the job.
But the point is that these programs are hyped over and over and taken as some kind of validation of Darwinian logic. So many experts can get it straight, it seems a strange self-deception.

Is evolution about to enter a new phase? Today, 300 biologists, computer scientists, physicists, mathematicians, philosophers and social scientists from around the world are gathering in Winchester. Their aim is to address one of the greatest challenges in modern science: how to create a genuine artificial life form.

Intelligent design: self-aware computers such as Pixar’s Wall-E are surprisingly tricky to put together

The idea that life owes its existence to some “vital essence” or “animating spark” has long been discredited in scientific circles. Instead, it is believed that the first living thing emerged after a chemical reaction crossed the watershed that divides inanimate objects from the kind of self-replicating “organic” reactions that run our cells.

Researchers into artificial life, or “ALife”, take two basic approaches. In “wet” ALife, scientists either tinker with microbes and other forms of simple life, or try to cook up cocktails of chemicals on water (hence “wet”) that have the capacity to extract energy and raw materials from the environment, to grow and reproduce, and ultimately to evolve. Meanwhile, “in silico” ALifers use silicon chips to try to kindle the spark of life in the heart of a computer.

In the latter field, a celebrated experiment was carried out almost two decades ago by Dr Thomas Ray, at the University of Delaware. He created the first successful attempt at Darwinian evolution inside a computer, in which organisms - scraps of computer code - fought for memory (space) and processor power (energy) within a cordoned-off “nature reserve” inside the machine.

His evocative experiment was called “Tierra”, after the Spanish for “Earth”. Back in 1993, when I met him in Oxford, it seemed to be a vital tool in helping us understand why the world is seething with diversity, from rainforest to coral reef.

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For evolution to occur, Dr Ray had to allow his programs to mutate. The “Tierran” programming language he devised was robust enough that it could often work after mutations. He also had natural selection: a program called the reaper killed off old and faulty software, enabling more successful organisms to monopolise resources.

On January 3 1990, he started with a program some 80 instructions long, Tierra’s equivalent of a single-celled sexless organism, analogous to the entities some believe paved the way towards life. The “creature” - a set of instructions that also formed its body - would identify the beginning and end of itself, calculate its size, copy itself into a free region of memory, and then divide.

Before long, Dr Ray saw a mutant. Slightly smaller in length, it was able to make more efficient use of the available resources, so its family grew in size until they exceeded the numbers of the original ancestor. Subsequent mutations needed even fewer instructions, so could carry out their tasks more quickly, grazing on more and more of the available computer space.

A creature appeared with about half the original number of instructions, too few to reproduce in the conventional way. Being a parasite, it was dependent on others to multiply. Tierra even went on to develop hyper-parasites - creatures which forced other parasites to help them multiply. “I got all this ecological diversity on the very first shot,” Dr Ray told me.

Other versions of computer evolution followed. Researchers thought that with more computer power, they could create more complex creatures - the richer the computer’s environment, the richer the ALife that could go forth and multiply.

But these virtual landscapes have turned out to be surprisingly barren. Prof Mark Bedau of Reed College in Portland, Oregon, will argue at this week’s meeting - the 11th International Conference on Artificial Life - that despite the promise that organisms could one day breed in a computer, such systems quickly run out of steam, as genetic possibilities are not open-ended but predefined. Unlike the real world, the outcome of computer evolution is built into its programming.

His conclusion? Although natural selection is necessary for life, something is missing in our understanding of how evolution produced complex creatures. By this, he doesn’t mean intelligent design - the claim that only God can light the blue touch paper of life - but some other concept. “I don’t know what it is, nor do I think anyone else does, contrary to the claims you hear asserted,” he says. But he believes ALife will be crucial in discovering the missing mechanism.

Dr Richard Watson of Southampton University, the co-organiser of the conference, echoes his concerns. “Although Darwin gave us an essential component for the evolution of complexity, it is not a sufficient theory,” he says. “There are other essential components that are missing.”

One of these may be “self-organisation”, which occurs when simpler units - molecules, microbes or creatures - work together using simple rules to create complex patterns and behaviour.

Heat up a saucer of oil and it will self-organise to form a honeycomb pattern, with adjacent “cells” forming as the oil turns by convection. In the correct conditions, water molecules will self-organise into beautiful six-sided snowflakes. Add together the correct chemicals in something called a BZ reaction, and one can create a “clock” that routinely changes colour.

At the Winchester conference, Prof Takashi Ikegami, from the University of Tokyo, will explain the ways that self-organisation operates among birds, to help them form flocks, and in robots, children, flies and cells, too. Another keynote speaker will be Prof Peter Schuster of the University of Vienna.

With the Nobel Laureate Manfred Eigen, he came up with the idea of the “hypercycle” - different components “feeding on each others’ waste” while maintaining an (often fragile) overall stability. This scheme was used to show how simple chemicals co-operated to create the first living things billions of years ago.

“Evolution on its own doesn’t look like it can make the creative leaps that have occurred in the history of life,” says Dr Seth Bullock, another of the conference’s organisers. “It’s a great process for refining, tinkering, and so on. But self-organisation is the process that is needed alongside natural selection before you get the kind of creative power that we see around us.

“Understanding how those two processes combine is the biggest challenge in biology.”

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