The 1918 H1N1 pandemic, known as Spanish Flu, is one of the deadliest pandemics on recorded history. It is estimated that the Spanish Flu pandemic affected over 500 million people across the globe, and the death toll is estimated to be between 20 to 50 million. Ever since this, scientists worked hard to find an effective vaccine for influenza, but its very rapidly evolving nature made this task quite the challenge. In this thesis we performed molecular evolution and population genetics analyses on 35714 hemagglutinin and 36302 neuraminidase nucleotide sequences to better understand the evolution of these proteins. The Tajima’s D values showed strong positive selection on the pandemic year of 2009 and the BEAST analysis results also suggested there was a greater exponential growth compared to other years. The relaxation of selection and lack of exponential population growth was inferred from the calculations for 2021 sequences, whereas the positive selection on the hemagglutinin and neuraminidase proteins was evident for the 2022 sequences. Outgroup tests also confirmed the positive selection was acting on the pandemic and non-pandemic years, the tests also confirmed the divergence of human influenza neuraminidase from the swine influenza neuraminidase. HA2 part of hemagglutinin and 475-500 nt part of neuraminidase proteins were found to be the most conserved parts of these proteins. In conclusion, the positive selection on these two proteins returned after the year 2021, which was a very unusual year for influenza that caused the positive selection on the virus and the exponential growth rates of the virus to decline. The most conserved regions can be a good candidate for small molecule/drug and vaccine studies.