Sequence of both $m t$ DNA and $\mathrm{Y}$ chromosomes are considered for the study of human evolution because they are uniparental in origin. mtDNA is inherited along with the maternal cytoplasm and $\mathrm{Y}$ chromosome is inherited from father. So they do not take part in recombination. In addition, mtDNA has a higher mutation rate then nuclear DNA so that it is more useful for short term evolutionary studies.
Related Theory
The Ychromosomeisinheritedfromthefather; therefore, paternal social class was included in the Y chromosome analysis. Mitochondrial DNA is inherited from the mother; thus, maternal social class was included in the analysis along with paternal social class for mitochondrial DNA. More than $27 \%$ of the variance in Y-haplogroups can be attributed to differences between populations, whereas mtDNA showed much lower heterogeneity between populations (less than 5\%), suggesting a strong influence of patrilocal social structure.