Believe it or not, this isn’t a human embryo. Or a dog embryo. Or a giraffe embryo. It’s not an embryo at all, but a newborn animal already out of the womb and in the world! This is a real photo of an opossum joey, taken moments after birth.
At a glance, newborn opossums look almost indistinguishable from the young of placental mammals early in gestation. If you put this photo side-by-side with pictures of rats, cats, and humans in the first 12 days after conception, you probably wouldn’t be able to tell the difference. But, while we depend on nutrition and oxygen from the placenta for many months, an opossum joey needs none of that! They go right from being jellybean-sized embryos to being born, skipping the fetal stage entirely!
Despite being so tiny and squishy and formless, opossums are born with claws that enable them to grasp the mother’s hair and skin, and a strong sense of gravity that tells them to start the journey up from her pseudo vaginal canal toward her nipples. From there, they instinctively find a teat and swallow it. Opossum joeys stay attached to their mothers’ nipples for several weeks and then start to emerge from the pouch.
It’s incredible to share a planet with animals who are so much like us, and yet so different! We start the beginning of life looking nearly identical, but the way we grow and develop is dramatically different. How amazing is that?