'The bird’s Egg', a short essay by Dr James le Fanu once in The Oldie, does make me wonder about irreducible complexity
......... there is certainly perfection in how the yolk contains all these nutrients in precisely the right amounts and proportions, but more perfect still, is how the egg acquires through its seemingly impermeable shell the only vital requirement from the outside world for the embryo’s development – oxygen. The egg’s ability to ‘breathe’ is determined by the shell’s method of construction. The arrival of the yolk and enfolding ‘white’ in the uterus activates dozens of tiny aerosol sprays that squirt a concentrated solution of calcium carbonate. The solution hardens to form columns of calcite packed against each other ‘like a stack of fence posts’ and separated by tiny vertical spaces – or microscopic pores. This method of construction might
seem a bit haphazard but the ‘total pore area’ – their number multiplied by their diameter – must be precisely calibrated to ensure the correct flow of gases in and out of the shell: too high and the oxygendependent metabolism goes into overdrive, too low and the embryo within will suffocate through lack of oxygen or be poisoned by the accumulation of carbon dioxide. Thus the ‘total pore area’ of the ten thousand pores in the shell of a 60g chick’s egg is determined by its requirement, over the 21 days of its incubation, to take up six litres of oxygen and expel as waste products 4.5 litres of carbon dioxide and 11 litres of water vapour. The volume of gases exchanged are, biologist Hermann Rahn discovered in the 1970s, perfectly ‘attuned’ to the size of the embryo with a direct correlation between the total pore area and the mass of the egg ..........