PLAYING GOD

The New York Times goes backward in time to review mechanisms that may have contributed to the spark of life on Earth.

Living cells are generally impermeable and have elaborate mechanisms for admitting only the nutrients they need. But Dr. Szostak and his colleagues have shown that small molecules can easily enter the protocells. If they combine into larger molecules, however, they cannot get out, just the arrangement a primitive cell would need. If a protocell is made to encapsulate a short piece of DNA and is then fed with nucleotides, the building blocks of DNA, the nucleotides will spontaneously enter the cell and link into another DNA molecule. - NYT

Meanwhile at New Scientist, they review the impact of life on the planet's history through the theory of Gaia and postulate on the planets death through the principles of Medea.

The starting point is that the sun is getting hotter. It has increased in brightness by about 30 per cent over the past 4.5 billion years and will carry on doing so. As the sun continues to burn brighter it will cause global warming, which will translate into increased weathering of silicate rocks - the rate of weathering rises with temperature. This will remove CO2 ever faster from the atmosphere, aided and abetted by photosynthesis and plant roots. Calamity strikes

At first, this removal of CO2 will buffer the solar-induced temperature increase. But there will come a time - possibly as early as 500 million years from now - when there is not enough CO2 in the atmosphere to support photosynthesis. When that calamitous day arrives, a very pronounced end of the world as we know it will begin.

The changes will be dramatic and catastrophic to life. Plants will wither and die, shutting off the main source of biological productivity and atmospheric oxygen. Animals will quickly follow. The loss of plants will also lead to a renewed build-up of CO2 in the atmosphere, leading to a runaway greenhouse. Eventually, the temperature of the Earth's surface will exceed that of boiling water, and the last microbe will perish. Earth will be lifeless once more. This is very anti-Gaian, since the theory states that the presence of life on a planet should extend its habitability. The opposite is true.

If these models are correct, life on Earth is already in its old age. The adventure that started 3.8 billion years ago, and is still the only life we know of in the universe, has maybe another billion years to run. The long-term, and terminal, decline of CO2 in the atmosphere has already started - the effect of burning fossil fuels is just a blip. Gaia is dying. Long live Medea. For now. - NS