Gary Marcus wrote a book called The Birth of the Mind about how a small number of genes builds a complex brain.

True: Gary Marcus is the author of The Birth of the Mind (Basic Books, 2004), and the book's subject is how a relatively small number of genes can build a complex brain. Mostly true: he wrote the book, and its theme is about genes and brain development, but the summary in the claim is a slight simplification. Mostly false: he wrote the book, but its subject is materially different from the description. False: he did not write a book by that title.

Set before the research began.

1. E1 The Birth of the Mind by Gary Marcus | Hachette Book Group Hachette Book Group / Basic Books · 27 June 2017

   “Synthesizing up-to-the-minute biology with his own original findings on child development, Marcus is the first to resolve this apparent contradiction by chronicling exactly how genes create the infinite complexities of the human mind.”

2. E2 The birth of the mind: How a tiny number of genes creates the complexities of human thought. By Gary Marcus. New York: Basic Books, 2004. Pp. 278. ISBN 0465044050. $26. | Language | Cambridge Core Cambridge University Press (Language journal, Linguistic Society of America) · December 2006

   “The birth of the mind: How a tiny number of genes creates the complexities of human thought. By Gary Marcus. New York: Basic Books, 2004. Pp. 278. ISBN 0465044050. $26.”

3. E3 The new nativism: a commentary on Gary Marcus's The birth of the mind - Biology & Philosophy Springer (Biology and Philosophy) · 10 November 2006

   “Gary Marcus (2004) has written a very interesting book about mental development from a nativist perspective.”

The claim holds up. A book-review listing in the journal Language [E2] names Gary Marcus as the author of "The birth of the mind: How a tiny number of genes creates the complexities of human thought" (New York: Basic Books, 2004). The publisher's page [E1] says the book chronicles "how genes create the infinite complexities of the human mind," and an academic commentary [E3] calls it a book about mental development. Together these confirm that Marcus wrote it and that its subject matches his description: a small number of genes building a complex mind or brain.