Alfred Henry Sturtevant studied heredity in fruit flies in the US throughout the twentieth century. From 1910 to 1928, Sturtevant worked in Thomas Hunt Morgan’s research lab in New York City, New York. Sturtevant, Morgan, and other researchers established that chromosomes play a role in the inheritance of traits. In 1913, as an undergraduate, Sturtevant created one of the earliest genetic maps of a fruit fly chromosome, which showed the relative positions of genes along the chromosome. At the California Institute of Technology in Pasadena, California, he later created one of the first fate maps, which tracks embryonic cells throughout their development into an adult organism. Sturtevant’s contributions helped scientists explain genetic and cellular processes that affect early organismal development.

Petr Kropotkin proposed the theory of Pleistocene ice age, alternative theories of evolution based on embryology, and he advocated anarchist and communist social doctrines in Europe during the nineteenth and twentieth centuries. He traveled in eastern Siberia and Manchuria from 1863 until 1867, and his subsequent publications about that area's geography became authoritative until the middle of the twentieth century. Kropotkin argued that his geographic and geologic observations in Asia, Finland, Sweden, and Canada, supported the theory of Pleistocene continental glaciation, often called the ice age. He was one of the first to study the ancient geography and climate of the Quaternary period, which spans from 2.5 million years ago until the present. Around the turn of the nineteenth century, Kropotkin offered what he said were complementary amendments to Charles Darwin's 1859 theory of evolution by natural selection. Kropotkin employed a variety of arguments from natural history, embryology, and geography to support his theory of mutual aid, which he argued was a positive mechanistic addition to the theory of evolution.

The Inheritance of Acquired Characteristics is a book published in 1924, written by Paul Kammerer, who studied developmental biology in Vienna, Austria, in the early twentieth century. The Inheritance of Acquired Characteristics summarizes Kammerer's experiments, and explains their significance. In his book, Kammerer aims to explain how offspring inherit traits from their parents. Some scholars criticized Kammerer's reports and interpretations, arguing that they were inaccurate and misleading, while others supported Kammerer's work. Kammerer said that the results of his experiments demonstrated that organisms could adapt to different environments by acquiring new features during the course of their lifetimes, and that they transmitted those acquired features to their offspring.