Although penguins' ancestors could certainly fly many eons ago, the birds that developed shorter wings with fine dense feathering, and heavy layers of body fat to protect them from the cold, were able to better survive 
(penguins' ancestors; could certainly fly; many eons; T:ago) (the birds; developed; shorter wings) (the birds that developed shorter wings with fine dense feathering, and heavy layers of body fat to protect them from the cold,; were; able to better survive) (the birds that developed shorter wings with fine dense feathering, and heavy layers of body fat to protect them from the cold,; to better survive; )
penguins' ancestors the birds the birds that developed shorter wings with fine dense feathering, and heavy layers of body fat to protect them from the cold, the birds that developed shorter wings with fine dense feathering, and heavy layers of body fat to protect them from the cold,
could certainly fly developed were to better survive
many eons T:ago
shorter wings
able to better survive