In the late 19th century it came to mean the concept that natural selection was the sole mechanism of evolution , in contrast to Lamarckism , then around NUMBER@1 it was eclipsed by Mendelism until the modern evolutionary synthesis unified PERSON@1 's and PERSON@2 's ideas .

In the late 19th century it came to mean the concept that natural selection was the only mechanism of evolution , in contrast to Lamarckism .
