There is so much going on in DNA studies – even if pre-figured by linguistic studies – that having a solid guide to stitch it all together, including papers that landed with a giant thud in 2018, would be so very, very nice. Someone who could put it together for the layman or intelligent observer who finds it hard to sort through headlines and the latest pronouncements (and simplifications). Fortunately, Tony Joseph's Early Indians fits the bill mightily. It brings together many lines of research centering around ancient and modern DNA studies in a lucid, engaging way that makes complex concepts easier to understand. One comes away with a clear recognition that Indian genetic history is mixed and multi-layered – there is nothing "pure" here as people who gravitate towards the simplifications of "racial purity" may wish. One also comes away with a much deeper and more rigorous understanding of what makes South Asia's populations and its base and "flavoured" genomes so unique in world history.

An overarching theme is that archaeology, linguistics and genetics are converging. If the archaeological evidence was a bit light and theoretical (Mehrgarh as prime example of initial movement from Zagros Mountains of agriculturalists and practices between 7000 and 3000 BCE into the subcontinent), the linguistic story much stronger (e.g. Sanskrit's Indo-Aryan roots from Central Asian migrations between 2000 and 1000 BCE), the genetic evidence over the past decade – and especially in the last few years – overwhelmingly supports and reinforces what these two other fields of study are showing. It adds finer detail and contour, and opens up new questions. At the same time, the book is careful to not confuse language and people; the origin of Dravidian languages in the Iranian plateau does not mean that the genes of those speaker predominate in areas where Dravidian is spoken today (just as the use of English in the region today may not involve but a wisp of European DNA). It is all very complex, but Tony Joseph proves to be a clear, careful and engaging guide through a thicket of studies, and the picture he draws, while simplified in some parts, is true to the material as it stands today.

Joseph is particularly fond of the pizza metaphor, which he introduces at the beginning, and by the end of the book does not seem so far off: "One way to understand the population structure of today's India [really South Asia] is to think of it as a pizza, with the First Indians forming its base. Some parts of the pizza are think crust, some parts thick crust, but al parts need to have the base – the pizza doesn't exist without it. Then comes the sauce that is spread all over the pizza. And then the cheese and the toppings – the people who came into the subcontinent later, at various periods. The cheese and the toppings are not uniform across the different slices. Some slices have an extra topping of tomato, some have more capsicum and others a lot of mushroom. The sauce, the cheese or the toppings that you find on this Indian pizza are not unique; these are found in other parts of the world too – some in West Asia, some in Southeast Asia and some in Europe and Central Asia. But the base of the pizza is unique to India – you will not find another one like it anywhere else in the world. And neither will you find a pizza with this level of diversity in any place other than Africa" (p. 61).

The best thing about this book is that it gives a clear picture of how the evidence stacks up for the original development of the "First Indian" population who came out of Africa 50-60,000 years ago, the agriculturalist move into Balochistan (and perhaps elsewhere) that likely helped spark the Indus civilization, and the Aryan migration that followed on the heels of the Indus civilization's decline. It also answers questions about the Andaman Islanders for example, or the migration into India of smaller populations from Southeast Asia and China into the eastern subcontinent and Myanmar – no, it was not a continuous western movement from recent DNA evidence in pre-historic times, people actually moved into eastern India from China and Southeast Asia (things changed later when Indian religions and cultural practices moved further westward and northward all the way to Indonesia and China). He also debunks very nicely many myths, like an 'out-of-India' movement of languages and people by using the Romani (gypsy) example from roughly the 10th century ACE to show how such a westward migration from the subcontinent, had it happened earlier on a large scale, would have left far deeper DNA and other evidence.

Joseph is also to be complimented for taking the bull (or should it be the water buffalo?) by the horns when it comes "to the special sensitivity to the question about the arrival of Indo-European-language speakers? The answer is simple: it is the unstated by underlying assumption that Indian culture is identical or synonymous with 'Aryan', 'Sanskrit' or 'Vedic' culture. Therefore to ask when Indo-European languages reached India would be seen to be asking the same thing as asking 'when did we import our culture?'"

He continues: "But this is ridiculous on two counts. First of all, Indian culture is not synonymous with, or identical to, 'Aryan' or 'Sanskrit' or 'Vedic' culture. 'Aryan' culture was an important stream that contributed to creating the unique Indian civilization as we know it today, but by no means was it the only one. There were other streams that have contributed equally to making Indian civilization what it is. Second, to say that Indo-European languages reached India at a particular historical juncture is not the same as suggesting that the 'Vedas' or 'Sanskrit' or the 'Aryan' culture was imported flat-packed and then reassembled here. 'Aryan' culture was most likely the result of interaction, adoption and adaptation among those who brought Indo-European languages to India and those who were already well-settled inhabitants of the region" (p. 162-163).

This final point is so important and defies the simplifications that people allergic to any Central Asian migration often miss - Indus and other cultures mixed and persisted in what has become the rich distribution of cultures in the region today. It is all about mixing and creating hybrid forms as much as it is, maybe less so, about supplanting, just as it is today. What is very interesting (and disturbing) in Joseph's retelling of the DNA story though is not only how Central Asian DNA strands seem much more predominant in certain higher castes, but also how much male DNA (Y-chromosome lineages), especially in North India, seems to have much higher traces of Central Asian DNA, whereas female mitochondrial DNA (mtDNA) has less and, in general, is more similar to 'base' Indian DNA. In other words he quotes a 2017 paper to say that "70 to 90 percent of mtDNA lineages of present-day Indian populations derive from First Indians, while only 1- to 40 percent of Y-chromosome lineages have similar ancestry. This difference is attributable to sex bias in later migrations" (p. 181-2). This follows a pattern seen elsewhere in the world, and suggests that male invaders or migrants dominated the influx and took local women as brides or otherwise had children with them. While we have no direct evidence of how this happened, evidence from Europe and especially Central Asia often point to rape or forced marriage as the method (with male inhabitants slaughtered or certainly not procreating to the same extent).

Joseph has taken care to examine all the major books and studies in this field, and includes points-of-view that diverge from his or most received opinion among DNA experts. His quote from David Reich, whose lab at Harvard has pioneered many of these DNA studies is particularly apt: "People tend to think of India with its more than 1.3 billion people as having a tremendously large population, and indeed many Indians as well as foreigners see it this way. But genetically, this is an incorrect way to view the situation. The Han Chinese are truly a large population. They have been mixing freely for thousands of years. In contrast there are few if any Indian groups that are demographically very large, and the degree of genetic differentiation among Indian jati groups living side by side in the same village is typically two or three times higher than the genetic differentiation between northern and southern Europeans. The truth is that India is composed of a large number of small populations" (David Reich, Who We Are and How We Got There).

This is an extraordinary statement to ponder, even more so when we include neighbouring modern populations (Pakistan, Bangladesh, Nepal, Sri Lanka) for whom the same is true and which add at least another 400 million to the equation. This is the largest, most genetically diverse pool of people on earth.

Is this the end of the story? Certainly not. Much more research needs to be done, especially with DNA of ancient Indus and other Bronze Age and pre-Bronze Age populations. One might conjecture that the agriculturalist move from the Zagros mountains had many tentacles, and fits and starts, perhaps reflected in things like the Kulli and other cultures abutting the ancient Indus valley that we have not yet understood. If the recent past is prologue, there are many surprises to come, many discoveries to be made. This is an ongoing story, and Tony Joseph has provided a wonderfully engaging and sophisticated lens to start understanding and absorbing all this information through. He writes specifically for an Indian audience, but the closing lines of his book are applicable to the entire South Asian population world: "We are all Indians. And we are all migrants."