Table 2.

Fraction of random codes that are fitter than the genetic code

f	ΦFH	Φequif	Φfaa
gpol	9.8 × 10-7	1.5 × 10-6	6.5 × 10-7
gaccess	1.7 × 10-6	1.9 × 10-6	1.2 × 10-6
gcode	3.4 × 10-15*	5.1 × 10-16*	5.0 × 10-17*
gPAM	3.8 × 10-6	2.2 × 10-6	2.0 × 10-9
gmutate	2.3 × 10-6	6.0 × 10-7	2.0 × 10-9

Fraction f of random codes that have a lower value of the fitness functionΦ^FH, Φ^equi or Φ^faa) than the natural code, using each of the four cost functions g^pol, g^access, g^code, g^PAM and g^mutate. Values marked with an asterisk have been obtained by extrapolation as explained in text. The number of randomly generated codes is equal to 10⁹ and the amino-acid frequencies used are the average ones listed in the right-hand column of Table 1.