GOP frontrunner Ben Carson, in a 1998 commencement address, floated his own personal theory that the pyramids in Egypt were built by Joseph — the biblical patriarch known for his coat of many colors — to store grain, Buzzfeed reported.

In the speech — given at Andrews University, a school with ties to Carson’s Seventh-day Adventist faith — the neurosurgeon shot down claim that aliens had built the pyramids. But he also disagreed with the archaeological consensus that the pyramids were constructed as tombs for the pharaohs.

“My own personal theory is that Joseph built the pyramids to store grain,” Carson said. “Now all the archeologists think that they were made for the pharaohs’ graves. But, you know, it would have to be something awfully big if you stop and think about it. And I don’t think it’d just disappear over the course of time to store that much grain.”

In the video surfaced by Buzzfeed Wednesday, Carson goes on to lay out his argument that the pyramids were constructed for grain storage.

“And when you look at the way that the pyramids are made, with many chambers that are hermetically sealed, they’d have to be that way for various reasons,” Carson said. “And various of scientists have said, ‘well, you know there were alien beings that came down and they have special knowledge and that’s how-’ you know, it doesn’t require an alien being when God is with you.”