Here are some examples taken from Jeff Harring's 3 day (!!!) workshop "INTRODUCTION TO FINITE MIXTURE MODELS; he pointed me to the 1st mixture modeling idea, published in 1894 (!)
Pearson, K. (1894). Contributions to the mathematical theory of evolution. Philosophical Transactions of the Royal Society of London. A, 185, 71-110.
* Here are also other ways of gauging if one has more than 1 population in their data:
or by looking at the random slopes and intercepts: