Happy Spring Equinox, or Ostara!  Of course, our spherical planet also gives us the beautiful symmetry of the  Fall Equinox (& Mabon) being celebrated now by our Southern Hemisphere friends.  The moment of the Equinox is at 5:58 pm (EDT), Wednesday, March 20th.  Life returns!

Life is an amazing development, with so much complexity that we are constantly learning and understanding more about it.  One of those many amazing features is sexual reproduction.  The sex part is more of a Beltaine focus, of course, but combining different and new DNA raises all kinds of difficulties in making a new organism – which is the new life we celebrate today with Ostara.  Amid all the eggs and bunnies, it’s easy to forget the challenges that evolution has overcome (and continues to wrestle with) when it comes to eggs and babies.

It hard shelled egg itself is a great solution to the very difficult problem of living full time on the land.  This is because eggs had to be laid underwater to both keep them wet as well as to get oxygen.  What an insurmountable barrier!  A solid shell around the eggs would suffocate them in a matter of hours, but without a shell they would die of dehydration even faster than that.  What to do?  ~300 million years ago, our reptile ancestors conquered the land with the evolution of a crusty, yet gas permeable, egg shell.

As humans, we still hatch from eggs.  What?  No, really.  After the hard shelled egg allowed our reptile Ancestors to spread over the land, our early mammal Ancestors had even better survival rates by keeping the eggs inside the body until they hatched.  Mutations eliminated the formation of the shell, but the thin membrane of the egg itself still forms, and when the baby hatches, the fluid in that egg is no longer contained – that’s what we now call “water” – “breaking” before birth.

The egg as a cell (no shell nor membrane) goes back to jawed fish or earlier, long before life on land.  Sexual reproduction introduces the problem of a living cell inside the body which has different DNA than the mother (half being from the father) and hence prompting an immune response.  This means that each step which kept that embryo inside the body for more time was an additional challenge to overcome.  Many of these hurdles – one after another in our Ancestry – are described here.   Even back at the egg laying stage, this meant that layers of secretions around the embryo were needed to prevent the mother’s immune system from launching an attack against it.  Imagine how much harder this became once the baby was kept inside as it grew!  It turns out that we are only beginning to learn all of the mechanisms which have evolved to solve this problem (and they are of course beyond the scope of a post wishing you a Happy Ostara), but they include progesterone and other hormones affecting the mother’s entire immune system, and experience of the world.  This is related to why morning sickness evolved – better to make mothers hypersensitive to foods than to risk the chance of ingesting something which might hurt the embryo.

When these challenges were thus taken to a whole new level, the evolution of the placenta gave us an incredible solution.  Look at what the placenta’s job description: pass nutrients and oxygen from the mother’s body to the fetus, AND pass waste materials from the fetus to the mother’s body, both without allowing any cells from the mother to get to the baby, nor cells from the baby  to get to the mother (either of which could trigger an immune system attack).  Impossible!!  Worse, it’s only a temp position.  This whole new organ is grown early in the pregnancy, only to be disposed of a few months later.  A disposable organ!  Both the uterus which contains all this, and the whole system (and all the massive DNA changes which were needed), are truly wonders of evolution.

Celebrations

Some of the ways many of us are celebrating were published a few weeks ago. My family will celebrate the Equinox Sunday, with the egg coloring and other traditions mentioned in the post just linked to.  We have found that leaving them in the dye in the cold garage over night deepens their color.  In whatever way you are celebrating, Happy Equinox!

This is an  updated version of the yearly Spring Equinox announcement.   An overview of the eight holidays of the Wheel of the Year, from a naturalistic perspective, is here.