The mid-Holocene decline of hemlock populations is a much-studied phenomenon.[15] From its foundation in the early Holocene (c. 16,000 BP) in what is now the southeastern US, T. canadensis expanded rapidly and successfully into its potential range.[16] However, palynological analyses show the hemlock population experienced a pronounced decline approximately 5,500 BP that lasted for about 1,000 years. Continued research points to other, though less dramatic, dips in Holocene hemlock populations.[15][17] Pathogens, insects, and climatic change, and a combination of these, have all been proposed to explain these anomalies. The eastern hemlock increased again after the major decline, but did not recover its former place as a dominant species.