7.2 The unicellular human: hard to believe but undeniable.

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We go back to an early stage in individual human development. From the day of conception every human being has gone through a brief unicellular existence before growing up to his later adult size and stature:

• nine months before our birth there has been a fleeting moment when you and I have been a microscopic little bag, filled with chromosomes, each of which consisted of one thread-like molecule, wound into a ball

• within days this first cell has turned into a most voracious little creature: grabbing molecules from its environment, thousands of them every second, and converting them for its own use. Replica's of the original cell were assembled at a giddy speed; the prescriptions for the moulds and modifications were delivered by messengers: strands of nucleic acid, copied from the chromosomes.

7.3 Specialisation of tissues and organs