Marcel Mauss obtained funding for him to go to Leningrad for one year to pursue studies in genetics with Nikolai Vavilov, whose lectures he had attended with great interest at the National Institute of Agriculture.
In 1940, Haudricourt was awarded a position in the new Centre national de la recherche scientifique, in its botany department, but he was disappointed by the research being done there, which relied on static classifications instead of an evolutionary approach espousing the new developments of genetics.
The nonconformist thesis was not accepted by the two reviewers (Albert Dauzat and Mario Roques) and so Haudricourt was not allowed to teach at the École pratique des hautes études.
[6] His study of the history of Chinese, Vietnamese and other East Asian languages draws on seminal insights.
De l'origine des tons en vietnamien[7] explains tonogenesis in Vietnamese and numerous other East and Southeast Asian languages and paved the way for the reconstruction of nontonal ancestors for the languages of Mainland Southeast Asia, such as Proto-Sino-Tibetan and Proto-Tai.
For instance, words in the zhà 乍 and zuó 昨 series (Middle Chinese: *dzraeH and *dzak, respectively) rhyme, as do words in the bì 敝 and piē 瞥 series (Middle Chinese: *bjiejH and *phiet).
A second major finding is his hypothesis that labiovelars existed in Old Chinese: "...it seems that scholars have overlooked the fact that some rhymes in the Analytic Dictionary only appear with velar initials (/k/, /kʰ/, /g/, /x/, and /ŋ/), for instance -iʷei [MC *-wej] 齊, -ʷâng [*-wang] 唐, -iʷäng [*-jweng] 清, -ʷâk [*-wak] 鐸, -iʷet [*-wet] 屑etc.