Similarities Between Sikhs and Punjabis of Pakistan: A Genetic Perspective

AbstractThe partition of Punjab in 1947 divided a historically interconnected population between India and Pakistan, with most Sikhs becoming concentrated in Indian Punjab and most Punjabi Muslims remaining in Pakistani Punjab. Although religious affiliation subsequently became an important social boundary, genetic evidence indicates that the populations on the two sides of the modern border share deep ancestry that predates both Sikhism and the partition of British India. This review examines genetic similarities between Sikh populations, particularly Jat Sikhs and other Punjabi Sikh communities, and Punjabis of Pakistan using evidence from autosomal short tandem repeats (STRs), mitochondrial DNA (mtDNA), HLA polymorphisms, population-genetic studies and ancient-DNA research. Sikh and Pakistani Punjabi populations share a common northwestern South Asian genetic background characterized by substantial ancestry related to ancient populations of the Indus region, South Asian hunter-gatherers, Iranian-related populations and later Steppe-related populations. Studies of Jat Sikhs demonstrate substantial autosomal genetic diversity, while mitochondrial studies of Pakistani Punjabis reveal a composite South Asian, West Eurasian and other Eurasian maternal ancestry. Ancient-DNA studies further demonstrate that populations associated with the Indus region contributed substantially to later South Asian ancestry and that Steppe-related ancestry entered South Asia during the Bronze Age. These findings provide a biological framework for understanding why Sikhs and Pakistani Punjabis can be genetically similar despite differences in religion and modern national identity. At the same time, social endogamy, caste/community structure, geographic differentiation and post-1947 demographic history have produced measurable genetic differences between particular communities. Overall, the evidence supports the interpretation that Sikhs and Pakistani Punjabis represent closely related branches of the broader Punjabi population rather than genetically separate peoples.Keywords: Sikh, Punjabi, Pakistani Punjabi, Punjab, population genetics, Jat Sikh, mitochondrial DNA, autosomal STR, HLA, Indus Valley, Steppe ancestry, genetic ancestry, partition of Punjab. 1. IntroductionPunjab is one of the most historically significant regions of South Asia. The geographical area traditionally known as Punjab extends across present-day Pakistan and northwestern India and has historically functioned as a corridor connecting the Indian subcontinent with Afghanistan, Central Asia and the Iranian plateau.The modern division of Punjab into Indian and Pakistani territories is relatively recent. The partition of British India in 1947 produced one of the largest population movements of the twentieth century and substantially reorganized the religious geography of Punjab. Indian Punjab subsequently became predominantly Sikh, whereas Pakistani Punjab became predominantly Muslim.From a population-genetic perspective, however, religious and national boundaries should not automatically be interpreted as biological boundaries.Sikhism emerged in Punjab approximately five centuries ago, whereas the major ancestral components of Punjabi populations developed over thousands of years. Consequently, the genetic similarities between Sikhs and Pakistani Punjabis are expected to be substantially older than the religious distinction between them.Modern population-genetic studies support this interpretation. Studies of Punjabi populations in Pakistan have identified extensive genetic diversity and ancestry derived from multiple Eurasian and South Asian sources [1,2]. Studies of Sikh populations similarly demonstrate substantial genetic diversity rather than a single distinctive Sikh genetic lineage [3–6].The purpose of this paper is to review the available evidence for genetic similarities between Sikhs and Punjabis of Pakistan. 2. Sikh and Punjabi Identity: An Important Genetic DistinctionA fundamental principle in population genetics is that religious identity does not necessarily correspond to biological ancestry.Sikhism developed within an already existing Punjabi population. Consequently, the ancestors of modern Sikhs were genetically related to the populations inhabiting Punjab before the emergence of Sikhism.Similarly, Pakistani Punjabis are not genetically defined by Islam. Pakistani Punjab contains numerous historical communities, clans and caste/tribal groups, including Jats, Rajputs, Arains, Gujjars, Awans and others.The 2024 HLA study of Pakistani Punjabis emphasizes that the Punjabi population is heterogeneous and includes numerous historically structured communities [1]. The study analyzed 389 Punjabi individuals and identified 162 HLA class-I alleles, demonstrating substantial genetic polymorphism. Therefore, a meaningful genetic comparison should ideally compare specific Punjabi communities, rather than treating all Sikhs or all Pakistani Punjabis as genetically homogeneous populations. 3. Shared Geographic OriginThe strongest basis for genetic similarity between Sikhs and Pakistani Punjabis is geography.The core region of Punjab extends across the modern international boundary. Major historical population centers such as Lahore, Amritsar, Gujranwala, Jalandhar, Ludhiana and adjoining regions were connected through migration, marriage, trade and political interaction for centuries.The modern international border was created only in 1947.Therefore:Modern border ≠ ancient genetic boundary.Population genetic variation generally changes gradually across geographic space rather than abruptly at recent political boundaries.This provides a strong expectation of substantial genetic continuity between Punjabis living in Indian and Pakistani Punjab. 4. Ancient Genetic Background Shared by PunjabisAncient-DNA research provides a deeper explanation for similarities between Sikh and Pakistani Punjabi populations.Narasimhan et al. analyzed 523 ancient individuals from South and Central Asia and demonstrated that the ancestry of present-day South Asians developed through interactions among several ancient populations [7]. Their results identified an important prehistoric ancestry gradient involving populations related to ancient Iranian hunter-gatherers and populations of South Asia. Following the decline of the Indus Valley Civilization, populations associated with the Indus region contributed to later South Asian populations, while Steppe-related ancestry subsequently entered South Asia through Central Asia. This is highly relevant to Punjab because much of the ancient evidence comes from the broader northwestern South Asian region.Consequently, both Sikhs and Pakistani Punjabis inherited ancestry from population processes that occurred thousands of years before the development of Sikhism or Islam in Punjab. 5. Indus-Related AncestryThe Indus Valley Civilization represents one of the most important ancestral layers in the genetic history of Punjab.Ancient genomic studies indicate that populations connected with the Indus region contributed substantially to the ancestry of later South Asians [7].Because Pakistani Punjab contains major archaeological regions associated with the Indus civilization—including sites in and around the broader Indus river system—the ancient Indus-related component is particularly important when considering the genetic ancestry of Pakistani Punjabis.Sikh populations of Indian Punjab also belong to the same broader northwestern South Asian genetic continuum.Therefore, both populations can share ancestry ultimately connected to ancient inhabitants of the Indus region. 6. Iranian-Related AncestryAnother important ancestral component is related to ancient populations associated with the Iranian plateau.This does not mean that modern Punjabis are simply descendants of ancient Iranians.Instead, ancient population movements produced genetic mixtures across the Iranian plateau, Central Asia and the Indus region.Narasimhan et al. showed that ancient populations related to Iranian hunter-gatherers formed part of the ancestry contributing to later South Asian populations [7]. Because both Indian and Pakistani Punjab are situated within the northwestern South Asian zone, this ancient ancestry contributes to the shared genetic background of both populations. 7. Steppe-Related AncestryAncient-DNA studies have also demonstrated the presence of ancestry related to Bronze Age Steppe populations in South Asia.Narasimhan et al. concluded that Steppe-related ancestry entered South Asia after approximately 2000 BCE, with movements through Central Asia contributing to the formation of later South Asian populations [7].Reich et al. previously demonstrated that many Indian populations possess ancestry related to an ancient component termed Ancestral North Indian (ANI), which has genetic affinities with populations of Central Asia, the Middle East and Europe [8]. Punjabi populations, including Sikh and Pakistani Punjabi populations, therefore belong to a broader northern South Asian genetic environment in which this ancestry is relevant.Importantly, Steppe ancestry should not be interpreted as evidence that either Sikhs or Pakistani Punjabis are a “Central Asian people.” It represents only one component of their complex ancestry. 8. Mitochondrial DNA SimilaritiesMitochondrial DNA is particularly useful for investigating maternal ancestry.Bhatti et al. analyzed 100 maternally unrelated Punjabi individuals from Pakistan belonging to Arain and Gujar communities [2]. They identified 58 mitochondrial haplotypes and found that Pakistani Punjabi maternal lineages represented a composite of South Asian, East Asian and West Eurasian ancestry [2]. The authors also reported substantial mitochondrial diversity together with a broadly homogeneous phylogeographic pattern across the Punjabi region.This finding is important for comparison with Sikh populations because it demon