This study was completed in order to examine whether the 677TT polymorphism exhibited adaptive developmental plasticity in 1818 South Indian subjects (895 males + 923 females). The frequency of MTHFR 677T was 9.1% in males + 11.0% in females. The 677T allele was highest in the 20-40 years age group, gradually decreasing as age increased. Furthermore, the 677T genotype was associated with 7 fold cumulative risk for Recurrent Pregnancy Loss, Neural Tube Defects + DVT. Males were shown to exhibit higher homocysteine levels, with each T allele attributed to a 4.63umol/ increase in homocysteine. Plasma homocysteine was inversely related to dietary folate, B2 + B6. Phenotypic plasticity is the ability of an organism (human) to change its phenotype in response to changes in the environment. The ability of one genotype to produce more than one phenotype when exposed to different environments.