Earth Obliquity and its effects on life

The angle Earth’s axis is tilted with respect to Earth’s orbital plane is known as obliquity and it significantly influences earth's climate, its weather patterns, and the natural rhythms of life. The Earth’s axis is currently tilted 23.4 degrees, or about half way between its extremes, and this angle is very slowly decreasing in a cycle that spans about 41,000 years.
Obliquity is why Earth has seasons. Over the last million years, it has varied between 22.1 and 24.5 degrees with respect to Earth’s orbital plane. More at NASA