 From studies across a number of species, it was estimated that 15–40% of all loci were polymorphic and the average individual was heterozygous at 5–15% of its genome. Since this technique measured primarily amino acid substitutions resulting in charge changes, i.e., only one third of all possible amino acid substitutions, one could infer that these were minimal levels of genetic diversity which significantly underestimated the actual levels. The conclusion that genetic variation was ubiquitous, with most genes being polymorphic, was inescapable. The search for the adaptive function of allozyme variants and balancing selection at the physiological level ensued, just as it had in the earliest studies in ecological genetics.