Jeff Dean, Google's chief scientist and one of its company's first employees, is leaving to launch his own company

Investors have been concerned that Google is trailing behind AI rivals, such as Anthropic and OpenAI.

Alphabet shares are dropping on Wednesday after the company announced a big shakeup at its artificial-intelligence division.

Jeff Dean, the chief scientist at Alphabet $(GOOG)$ $(GOOGL)$, is leaving the search-engine giant after 27 years to launch a public-benefit corporation focused on machine learning. Dean joined Google as its 30th employee in 1999 and is one of the architects of its AI strategy.

His replacement is Demis Hassabis, who will be stepping away from running the day-to-day operations at the DeepMind AI lab. He'll also take a new title as chair of Google DeepMind.

In a statement, Hassabis said the move will give him the "time and space focus on the big picture" around AI and artificial general intelligence, which could theoretically match or exceed human intelligence. Koray Kavukcuoglu, Google's chief AI architect, will now oversee the development of frontier AI research and the Gemini models.

Two other high-profile Google AI experts announced plans to leave the company in June. Noam Shazeer, who was the co-lead of Gemini said he was departing for OpenAI and John Jumper, a Nobel Prize winner, said he was moving to Anthropic.

The latest shakeup comes as delays on the Gemini models, combined with higher AI spending, have put pressure on Alphabet's stock. Shares fell by about 4% shortly after Google announced the transition. They fell 7% in the wake of the company's late-July earnings report, which brought heightened spending.

"We are the only company that has the full stack and we're world-class at every layer from infrastructure to cloud to frontier models to AI-first applications," Hassabis said in a statement.

"We have all the ingredients to lead from here, and I firmly believe we will," he added.

-William Gavin