An Indian burial ground was discovered by vacationers at the Malibu Ranch in 1908, according to the July 9th edition of the Los Angeles Times. The site on the Rindge property was near another cache of bones found a year earlier by railroad workers.
The upper half of a human skeleton was discovered by a 14-year-old Bruce Parsons in August 1922, while the Malibu Road was under construction (the Times speculated that bulldozers swept away the bottom half of the skeleton). The remains were carted off to Exposition Park and the museum.
USC maintains an archive of a dig uncovering more skeletons in 1956. This time, a bulldozer preparing ground for a real estate project uncovered the bones. That's where the above picture is from.
As recently as October 2007, a skull was discovered in Paradise Cove. Those remains, according to this article, were turned over to the Chumash tribe.
The rest ended up in museum storage for decades, until NAGPRA (Native American Graves Protection and Repatriation Act) came along.
A published notice of repatriation in accordance with NAGPRA rules was published in the Federal Register of Feb. 25, 2007, listing bodies found on the Malibu Ranch in 1915, by the Malibu Road in 1921, and several others that were found on unknown dates. Included are remains of four people found in Paradise Cove on an unknown date--as well as bodies found in Point Dume, Solstice Canyon, etc, and in Ventura and Santa Barbara County. 122 people in all, presumably now at rest.
I have always wondered--as particular as modern archaeologists are about details and paperwork--why is it taking so long to repatriate remains kept in storage? NAGPRA became law in 1990. That's 18 years already.
Malibu and points north were once dotted with Chumash villages. A map on page 1 of this 1996 report about skeletons excavated in the 1960s and 1970s shows dozens of identified villages.