The Palkeo Est were a humanoid species; their planet was seeded by the Progenitors, making them Descendants as well. Superficially, it was very difficult to tell the difference between a Palkeo and a human, save for their lighter features. Although these humanoids can blend in well with Terrans, distinct differences in their biology and physiology preclude the possibility of genetic hybrids from the two species.
The Palkeo Est evolved on the planet Altair III. Altair III's sister planet, the neighboring Altair VI, was once the host to the ancient civilization known as the Krell. The Krell had also colonized Altair III in the distant past, but fell victim to a plague which destroyed their civilization and wiped them out. It is believed by some that the Palkeo Est were descended from the Krell, although this theory holds very little merit in serious scientific discussion.
The Palkeo Est also colonized the planet Altair IV. In 2804 CE, the Palkeo Est made first contact with the Federation; following this, many human settlers would live on Altair IV and Altair III. They officially joined in 2825 CE. The Palkeo Est had their own embassy on the Citadel by 3040 CE.