(no entry for this year)

Fossil mammal expert William Diller Matthew suggests dinosaurs were driven extinct by mountain building, continental uplift and replacement by mammals.

Miners at Broken Hill in the British colony of Northern Rhodesia, Africa, find leg bones and a skull that will later be classified as Homo heidelbergensis.

Lillian V. Morgan discovers attached-X chromosomes in Drosophila.

The American Museum of Natural History begins a series of excavations in central Mongolia, led by Roy Chapman Andrews. Hoping to find fossil human remains, Chapman's team instead finds dinosaurs.

A. E. Boycott and C. Diver describe "delayed" Mendelian inheritance controlling the direction of the coiling of the shell in the snail Limnea peregra. A. H. Sturtevant suggests that the direction of coiling of the Limnea shell is determined by the character of the ooplasm, which is in turn controlled by the mother's genotype.

C. B. Bridges discovers chromosomal translocations in Drosophila.

Jesuit priests Émile Lincent and Pierre Teilhard de Chardin discover ancient stone tools at Shuidonggou, China. Their discoveries resemble those of the Middle Paleolithic industry in Europe.

Winifred Goldring publishes a description of a fossil forest discovered during excavations for the Gilboa Dam. Dating from the Devonian Period, the site will become known as the world's oldest fossil forest.

Tennessee schoolteacher John Thomas Scopes is tried for teaching evolution in the famous "Scopes Monkey Trial." Two-time presidential candidate William Jennings Bryan leads the prosecution. Labor lawyer Clarence Darrow leads the defense and goads Bryan into declaring that humans are not mammals. The conviction will be overturned on a technicality, and the anti- evolution law will remain on the books for decades.

A. H. Sturtevant analyzes the Bar-eye phenomenon in Drosophila and discovers position effect.

Francis Turville-Petre finds Galilee Man, the first fossil hominid discovered in Western Asia. The fossil will later be dated to more than 250,000 years old, and classified as neither modern Homo sapiens nor Neanderthal.

Raymond Dart publishes a description of the "Taung Child," a hominid child's skull from Africa. He classifies it as Australopithecus africanus and concludes that it's the missing link between humans and apes.

A. H. Sturtevant finds the first inversion in Drosophila.

Harvard geology professor William Morris Davis publishes a paper entitled The Value of Outrageous Geological Hypotheses warning against quick dismissal of new ideas. The paper will become famous.

Bernard O. Dodge initiates genetic studies on Neurospora.

H. J. Muller reports the artificial induction of mutations in Drosophila by x-rays.

J. B. S. Haldane suggests that the genes known to control certain coat colors in various rodents and carnivores may be evolutionarily homologous.

Excavations in Kent's Cavern in southern England turn up a fragment of a human upper jaw, roughly 43,000 years old. Arthur Keith will provisionally identify it as anatomically modern human, and this finding will be confirmed in a 2011 study.

Johns Hopkins University biologist Raymond Pearl publishes an article entitled "Why Lazy People Live the Longest." He will expand on this rate- of-living hypothesis in a book the next year, arguing that a faster rate of biochemical reactions leads to a shorter lifespan. This hypothesis is quickly dismissed and generally considered buncombe. Later, however, Donald Trump, the 45th president of the United States will be discovered to hold similar views.

Frederick Griffith discovers type-transformation of pneumococci. This lays the foundation for the work of Avery, MacLeod, and McCarthy (1944).

L. J. Stadler reports the artificial induction of mutations in maize, and demonstrates that the dose-frequency curve is linear.

In a letter to Science, Louise Sudbury states that fossil plants, Cycadeoidea Etrusca, were collected by Etruscans over 4,000 years ago.

In trying to piece together a Burgess Shale organism over 500 million years old, Danish zoologist K. L. Henriksen glues an Anomalocaris appendage to a Tuzoia carapace to make what he thinks is a reasonable looking shrimp-like animal. This mistaken interpretation will persist for years.

John Henry Pull, a postman and amateur archaeologist, finds fossil urchins in two separate Neolithic burial sites. His efforts to publish on his findings, however, will be thwarted due to his pedestrian background.

Davidson Black announces the find of Sinanthropus pekinensis, or Peking Man, discovered at Zhoukoudian, China. Over the next several years, five nearly-complete skulls will be recovered from the same site. Peking Man will be lost, however, during World War II.

Estonian paleobiologist Alexander Audova publishes a paper rejecting racial senility as the cause of dinosaur extinction and instead pointing to environmental change.