Linkage disequilibrium (LD) refers to the nonrandom association of alleles at different loci and is a key indicator of population genetic forces shaping a genome. It has become increasingly important in evolutionary biology and human genetics for understanding past events, mapping genes associated with diseases, and studying gene evolution. LD is more extensively used in humans than in non-humans, but this is changing with advances in genomic technologies. LD is defined by the difference between the frequency of gametes carrying specific alleles and the product of their individual frequencies. It reflects population history, breeding systems, and geographic subdivision, as well as natural selection, gene conversion, and mutation. The population genetics theory of LD is well developed and is used to study evolutionary history and map genes in humans and other species. LD can be affected by natural selection, genetic drift, recombination, and mutation. It is used to detect past selection events, estimate allele age, and infer population history. LD patterns vary among species and populations, with haplotype blocks being common in humans. These blocks are regions of strong LD and are important for gene mapping. LD is also used to detect population structure and bottlenecks, which can influence genetic variation. Other factors, such as inbreeding, inversions, and gene conversion, can also create LD. LD has practical applications in identifying disease-associated genes and understanding the genetic basis of complex diseases. However, challenges remain in accurately interpreting LD data, especially in non-human species. Advances in genomics and computational methods are improving the ability to study LD and its implications for evolutionary and medical research.Linkage disequilibrium (LD) refers to the nonrandom association of alleles at different loci and is a key indicator of population genetic forces shaping a genome. It has become increasingly important in evolutionary biology and human genetics for understanding past events, mapping genes associated with diseases, and studying gene evolution. LD is more extensively used in humans than in non-humans, but this is changing with advances in genomic technologies. LD is defined by the difference between the frequency of gametes carrying specific alleles and the product of their individual frequencies. It reflects population history, breeding systems, and geographic subdivision, as well as natural selection, gene conversion, and mutation. The population genetics theory of LD is well developed and is used to study evolutionary history and map genes in humans and other species. LD can be affected by natural selection, genetic drift, recombination, and mutation. It is used to detect past selection events, estimate allele age, and infer population history. LD patterns vary among species and populations, with haplotype blocks being common in humans. These blocks are regions of strong LD and are important for gene mapping. LD is also used to detect population structure and bottlenecks, which can influence genetic variation. Other factors, such as inbreeding, inversions, and gene conversion, can also create LD. LD has practical applications in identifying disease-associated genes and understanding the genetic basis of complex diseases. However, challenges remain in accurately interpreting LD data, especially in non-human species. Advances in genomics and computational methods are improving the ability to study LD and its implications for evolutionary and medical research.