The human eye is most sensitive to light in the green part of the visible spectrum due to a combination of factors related to our evolutionary history and the biology of our eyes.
1. Evolutionary Factors: Throughout human evolution, our ancestors relied on their ability to distinguish between different colors in natural environments. In many natural settings, green vegetation provided a significant source of sustenance and safety. Our sensitivity to green light likely evolved as an advantage, allowing us to better identify ripe fruits, healthy foliage, and potential threats hidden within green surroundings. 
2. Photoreceptor Distribution: Our retinas, the light-sensitive tissue at the back of our eyes, contain two main types of photoreceptor cells: rods and cones. Cones are responsible for color vision and are concentrated in the central part of the retina, known as the fovea. Cones come in three types, each sensitive to different parts of the color spectrum: short-wavelength (blue), medium-wavelength (green), and long-wavelength (red). 
3. Color Sensitivity: Among the three types of cones, the medium-wavelength cones (also known as M cones) are most sensitive to green light, specifically around the wavelength of 550 nanometers. This sensitivity allows us to detect and differentiate various shades of green with high accuracy. 
4. Contrast and Visibility: In natural environments, the prevalence of green, combined with our sensitivity to this color, enhances our ability to discern details and contrasts. This sensitivity contributes to improved visual acuity and the perception of depth, both of which are essential for survival and navigation.
Due to these evolutionary and biological factors, the human eye's heightened sensitivity to green light has persisted and influenced our ability to perceive and respond to our surroundings effectively. This sensitivity has practical implications in various fields, including visual arts, communication, and technology.