To celebrate the 40th anniversary of the first issue of Molecular Biology and Evolution, the Society for Molecular Biology and Evolution (SMBE) journals are publishing a series of virtual issues in 2024.These virtual issues contain selected papers published in the society's journals, Molecular Biology and Evolution and Genome Biology and Evolution.Each virtual issue is accompanied by a Perspective that highlights the historic and contemporary contributions of our journals to a specific topic in molecular evolution.

To celebrate the 40th anniversary of the first issue of Molecular Biology and Evolution, the Society for Molecular Biology and Evolution (SMBE) journals are launching a series of virtual issues in 2024.These virtual issues contain selected papers published in the society's journals, Molecular Biology and Evolution and Genome Biology and Evolution.Each virtual issue will be accompanied by a Perspective that highlights the historic and contemporary contributions of our journals to a specific topic in molecular evolution.

© The Author(s) 2023. Published by Oxford University Press on behalf of Society for Molecular Biology and Evolution. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. The course of human history has been marked by complex patterns of migration, isolation, and admixture, the latter a term that refers to gene flow between individuals from different populations. Admixture results in a blending of genetic lineages, leading to increased genetic diversity within populations. In addition to admixture among modern human populations, ancient humans reproduced with other hominin groups, such as Neanderthals and Denisovans. This resulted in fragments of DNA from these ancient lineages being passed down to modern humans in a process known as introgression. Two recent studies published in Genome Biology and Evolution examine patterns of admixture in two different regions of the world—Africa and the Americas—revealing how this process has shaped the genomes of modern humans. Africa is the birthplace of humanity, where our species originated and diversified. Because of this, Africa contains the highest levels of genetic diversity and population structure among humans, with non-African populations largely representing a subset of the genetic variation present on the African continent. Genomes of Africans contain mixtures of multiple ancestries, each of which has experienced different evolutionary histories. In the article “Evolutionary genetics and admixture in African populations,” researchers from two institutes—Georgia Institute of Technology and Mediclinic Precise Southern Africa—reviewed how multiple demographic events have shaped African genomes over time (Pfennig et al. 2023). According to Joseph Lachance, one of the review’s authors, “What stands out is the sheer complexity of human demographic history, especially in Africa. There are many examples of population divergence followed by secondary contact, the legacy of which is written in our genomes.” For example, ancient introgression from archaic “ghost” populations of hominins that are no longer extant contributed ∼4–6% of the ancestry of present-day Khoe-San, Mbuti, and western African populations. More recent demographic events that have occurred over the last 10,000 years have similarly resulted in admixture among modern humans, including gene flow among different click-speaking Khoe-San populations, the spread of pastoralism from eastern to southern Africa, and migrations of Bantu speakers across the continent. Importantly, biomedical studies often fail to capture this diversity, resulting in implications for the health and disease of those with African ancestry. A better understanding of genetic architecture can help predict disease risk in a population or even inform clinical decision-making for individual patients. Such information is critical for equitable biomedical research, leading the study’s authors to call for more ethically conducted studies of genetic variation in Africa. “A critical point right now is the relative lack of African genetic data,” says Lachance. “Most genomic studies have focused on Eurasian populations, and this limitation can exacerbate existing health inequities.” One avenue for better understanding, the genetic architecture of African genomes is the study of ancient DNA: “Going forward, analysis of ancient DNA is expected to become much more common. Future studies are also likely to focus on fine-scale population structure in Africa. However, logistical and financial obstacles persist. There is a clear need for funding mechanisms that build research capacity in Africa.” A second article recently published in Genome Biology and Evolution, titled “The impact of modern admixture on archaic human ancestry in human populations,” focuses on admixture in the Americas (Witt et al. 2023), which were colonized by modern humans relatively recently. The first people to enter the continent were Indigenous Americans who migrated from Siberia. Subsequent migration of Europeans and Africans due to European colonization and the Transatlantic slave trade resulted in admixed populations that combine ancestries from different continents. In the study, researchers from Brown University, the Universidad Nacional Autónoma de México, and the