Did the Buddha discover jhana by himself?

I was reading Ajahn Brahmavamso's book 'The Jhanas' (available freely online) in which he says that the Buddha discovered Jhanas by himself, and what Alara Kalama and Uddakha Ramaputta taught, were not related to jhana. The reason I am requesting your time is that, there are some teachers in Sri Lanka who claim that Jhanas are a later inclusion, citing the same fact that Alara Kalama and Uddaka Ramaputta were able to teach up to the highest immaterial Jhanas, and that a Samma Sambuddha couldn't have lent so heavily on the teaching of others for his own Enlightenment. Thus, they discourage samatha meditation. Fortunately such teachers still emphasize Sati. Would appreciate your thoughts.