Sir Herbert Hope Risley, a prominent British ethnographer and administrator during the colonial era, employed anthropometric methods to classify the diverse Indian population. His approach, rooted in 19th-century racial theories, involved taking precise physical measurements of individuals, such as skull shape (cephalic index), nasal index, stature, and facial features. Based on these measurements, he categorized Indian populations into seven primary racial types: Turko-Iranian, Indo-Aryan, Scytho-Dravidian, Aryo-Dravidian, Mongolo-Dravidian, Dravidian, and Mongoloid. Risley believed that these physical characteristics were indicative of distinct racial origins and often correlated with social hierarchies, particularly the caste system, which he attempted to explain through racial admixture.

Risley's classification, however, faced significant criticisms, both during his time and retrospectively:

1. Flawed Methodology: The primary criticism lies in the scientific validity of anthropometry as a basis for racial classification. Modern genetics has largely discredited the idea of fixed, discrete racial types based on physical traits. Human physical characteristics are continuous, not categorical, and are influenced by a complex interplay of genetics, environment, and diet, rather than pure racial lineage.
2. Racial Determinism and Justification of Hierarchy: Risley's work reinforced the notion of racial determinism, suggesting that physical traits determined social status and capabilities. This played into colonial narratives that sought to justify British rule and the existing social stratification, including the caste system, by attributing a biological basis to perceived differences.
3. Oversimplification of Indian Diversity: India's population is a product of millennia of migrations, intermingling, and cultural exchanges, resulting in immense genetic and phenotypic diversity. Risley's attempt to fit this complex reality into a few rigid racial categories was an oversimplification that ignored the intricate historical processes shaping Indian society.
4. Ethnocentric Bias: The classification was developed from a Eurocentric perspective, imposing Western racial categories and theories onto a non-Western population. It often projected European ideas of race onto Indian social structures, leading to misinterpretations.
5. Political Implications: Risley's classifications were not merely academic; they had significant political implications. They were used to support the 'divide and rule' policy of the British, by emphasizing differences and creating divisions among various groups based on perceived racial distinctions.
6. Lack of Genetic Basis: Contemporary genetic studies have demonstrated that genetic variation within so-called 'racial' groups is often greater than the variation between them. Risley's classifications do not align with modern understanding of human genetic diversity.

In essence, while Risley's work was influential in its time, it is now largely seen as a product of its era's pseudoscientific racial theories, lacking robust scientific foundation and contributing to the perpetuation of social inequalities.