Chapter 1: The Quest for Understanding Human Intelligence

Human intelligence stands as one of the most significant products of evolution, emerging from millions of years of development that resulted in larger brains and enhanced capabilities. While humans advanced to create societies and cultivate land, our primate relatives remained in their arboreal habitats. Recently, a team of scientists in southern China reported their endeavor to bridge this evolutionary divide. They have engineered transgenic macaque monkeys, incorporating additional copies of a human gene believed to influence intelligence.

Bing Su, a geneticist at the Kunming Institute of Zoology, spearheaded this groundbreaking research. He stated, “This represents the initial effort to explore human cognitive evolution through a transgenic monkey model.” Their research indicated that these modified monkeys excelled in a memory assessment involving color recognition and block patterns. Interestingly, their brain development was prolonged, similar to that of human children, although there was no notable change in overall brain size.

The findings, published on March 27 in the National Science Review and initially highlighted by Chinese media, do not unveil the intricacies of human cognition nor do they forecast a rise of highly intelligent primates. In contrast, several Western experts—including a collaborator from the study—deemed the experiments careless and raised ethical concerns regarding the genetic alteration of primates, an area where China has gained a technological advantage.

James Sikela, a geneticist focused on comparative primate studies at the University of Colorado, expressed his worries about the ethical implications of using transgenic monkeys to investigate genes associated with brain evolution. He warned, “This path is fraught with risks,” emphasizing the potential disregard for animal welfare and the likelihood of escalating genetic modifications.

Research involving primates faces increasing restrictions in Europe and the United States, but China is rapidly applying advanced DNA technologies to these animals. Notably, China was the first to employ CRISPR gene-editing tools on monkeys, and a recent announcement revealed the creation of clones of a monkey exhibiting severe mental disorders.

Chapter 2: Investigating the Genetic Foundations of Intelligence

The first video discusses Chinese scientists' groundbreaking work on inserting human brain genes into monkeys, shedding light on the implications for understanding intelligence.

Su, who specializes in identifying signs of “Darwinian selection,” has researched various topics, from the adaptation of Himalayan yaks to the evolution of human skin color. However, the most compelling mystery remains the nature of intelligence. Studies have indicated that the brains of our humanlike ancestors experienced rapid growth, prompting scientists to search for genetic variations between humans and chimpanzees, who share approximately 98% of our genetic material. Sikela highlights the goal of identifying “the jewels of our genome,” or the specific DNA that distinguishes us as humans.

One gene of interest is FOXP2, often referred to as the "language gene," due to its connection to speech capabilities. Notably, a family in Britain with a genetic mutation in FOXP2 experienced significant speech challenges. This spurred scientists globally to investigate the gene's influence by altering it in mice and analyzing their vocalizations.

Su turned his attention to a different gene: MCPH1, or microcephalin. Variations in this gene are linked to brain size, as individuals with microcephalin deficiencies are born with abnormally small heads. In a past study, Su and his team measured the head sizes of 867 individuals to examine genetic correlations.

In 2010, Su seized the opportunity to conduct a more definitive experiment—introducing the human microcephalin gene into monkeys. By then, China had established extensive breeding facilities for monkeys, which are crucial for scientific research.

To create these transgenic monkeys, Su and his collaborators at the Yunnan Key Laboratory of Primate Biomedical Research employed a virus carrying the human variant of microcephalin on monkey embryos. They successfully generated 11 monkeys, with five surviving to undergo various brain assessments. Each of these modified monkeys possesses between two to nine copies of the human gene.

The implications of these experiments raise significant ethical questions regarding animal rights. In 2010, Sikela and his colleagues published a paper on the ethics of utilizing transgenic non-human primates for studying human characteristics, concluding that altering the brains of apes, such as chimpanzees, poses ethical dilemmas due to their close genetic relationship to humans. Jacqueline Glover, a bioethicist at the University of Colorado and co-author of the paper, stated, “Humanizing them can lead to harm. What quality of life would they have?”

In correspondence, Su acknowledged the ethical concerns surrounding apes but argued that monkeys and humans diverged from a common ancestor 25 million years ago, which lessens the ethical implications. He believes that the modified monkeys will remain fundamentally monkey-like, asserting, “It’s impossible to transform them into something else by only introducing a few human genes.”

The second video delves into the ethical concerns sparked by human cells cultivated in monkey embryos, highlighting the complexities of genetic research.

Chapter 3: The Future of Genetic Research on Monkeys

Based on their research, the Chinese team anticipated that the transgenic monkeys would exhibit enhanced intelligence and larger brains. To investigate, they placed the monkeys in MRI machines to evaluate their white matter and conducted computerized memory assessments. While the modified monkeys did not show increased brain size, they performed remarkably well on a short-term memory test.

However, some scientists, including Martin Styner from the University of North Carolina, argue that the study did not contribute significantly to the field. Styner, who assisted in training Chinese students to analyze MRI data, considered distancing himself from the publication due to its inability to secure a Western publisher. He remarked, “There are aspects of this study that would not be permissible in the US,” raising concerns about animal welfare.

Styner expressed skepticism about the direction of transgenic monkey research, stating, “We’ve created an animal that deviates from its natural state. Our experiments must have a clear purpose to benefit society, which is currently lacking.” The high costs associated with creating and maintaining genetically modified monkeys complicate the pursuit of definitive conclusions about their cognitive abilities. With only five modified monkeys in existence, drawing reliable comparisons to typical monkeys is challenging.

Su conceded that the limited sample size is a drawback but expressed optimism about producing more monkeys and examining additional genes linked to brain evolution. One candidate, SRGAP2C—a genetic variant that emerged around two million years ago—has been dubbed the "humanity switch" and could play a pivotal role in the development of human intelligence.

Su is currently working to integrate this gene into monkeys, although it is too early to determine the outcomes of these efforts.

Antonio Regalado serves as the senior editor for biomedicine at MIT Technology Review, focusing on how advancements in technology are reshaping medicine and biomedical research. Prior to joining MIT Technology Review in July 2011, he reported on science, technology, and politics in Latin America while residing in São Paulo, Brazil.