Month: June 2020

About Giant Eggs & Double Yolks

This week’s gift from a neighbor’s chicken coop included one extra-large egg. After hard-boiling and cracking open we found a double yolk, which some say is a good omen on our wedding anniversary. The following conversation over a meal would be unlikely in most homes, but perfectly natural in ours.

“Have you ever seen a giant human egg?” I asked my wife, Lucinda Veeck. I have only had a few hundred eggs under my microscope, but Lucinda has examined tens of thousands over a long career in her IVF lab.

Chicken egg with double yolkShe said it happened once. It was obviously immature because there were two nuclei in a cell enclosed by a membranous ‘box’ (the ‘zona pellucida’). A normal egg contains one nucleus and it vanishes shortly before ripening at ovulation by ejecting a surplus set of chromosomes in a cytoplasmic bleb. This elimination is so a fertilizing sperm can add a matched set to restore the pair.

Now here’s the thing. Her giant egg was not a microscopic version of the cooked egg. If a hen bird ovulates two yolky eggs simultaneously, which happens occasionally, they are quickly bathed in albumen, then enclosed in a common membrane and a shell during their journey down the oviduct, a process that takes about 24 hours to laying. As the nuclei are in separate yolks, the outcome is a normal genetic makeup with two chicks hatching from the same egg, although the cramped space affects their viability . The closest parallel is when non-identical human twins are conceived after a double ovulation.

But the nuclei in Lucinda’s giant shared the same cell, so their DNA would be inherited together. Had it been mature for fertilization the embryo would likely have three sets of chromosomes (two female and one male), called digynic triploidy, and fail to develop.

We explored explanations for its origin. If you have seen densely packed eggs in biopsies of young human ovaries you might wonder how they manage to grow independently instead of being swayed by neighbors, like people jostled in a football crowd. Sometimes they lose autonomy. I have seen two or more eggs combined inside follicles of every species examined, up to 14 in dog ovaries, although some looked unhealthy from the competition.

When boxed inside their own membrane eggs can’t fuse to make giant eggs. They have unique genetic makeups, just like eggs from separate follicles that go forward to make non-identical twins. But what happens when they coexist in a ‘box’ and don’t fuse to form a single cell?

Lucinda saw an example five days after an IVF procedure. It was a double embryo at the blastocyst stage with about 64 cells each. If separated for implanting in the womb, it seemed likely they could make non-identical twins, but if they had originated from a fertilized egg that had split instead of from two separate eggs they would make identical twins. It’s possible that they could unite (or reunite) to make a singleton pregnancy, and, if originating from two fertilized eggs, the baby would inherit mixed genetic lineages, a known condition called chimerism.

In the interests of being (somewhat) intelligible, I avoided more abstruse explanations and outcomes. With so many ways that development can go awry, it is a marvel that we turn out well, or mostly, and I am thankful for my genesis otherwise you wouldn’t be reading this post. I usually avoid writing technical stuff, but correspondence is welcome from readers who like to crack eggs.

Next Post: The Sound of Noise & Silence

Into the Wild at Knepp Estate

Isabella Tree and her husband Charlie Burrell loved to travel from West Sussex to the fauna of wilder places in the world. No longer. They have re-envisioned their ‘backyard’ as semi-wilderness. Some backyard! They own the Knepp estate of 3,500 acres where, until the year 2000, they struggled to keep an arable and dairy farm out of the red, only turning a profit twice despite the tools and chemicals of intensive management.

The land was impoverished after centuries of farming the famously sticky Weald clay (local people have 30 adjectives for the mud). Vagaries in market prices and dependence on subsidies have plunged many small and mid-sized farms into bankruptcy, but they drew back from defeat with an original idea, though it inflamed tradition-bound rural neighbors.

They sold their livestock and farm equipment to let natural processes rule. People grumbled at the eyesore and wicked waste of food production, but over the next two decades the experiment in land ecology rolled forward to win plaudits. Isabella’s account of the makeover is acclaimed by the Daily Mail as the ‘most inspirational book of the year’ (2019).

The couple was inspired by the Dutch ecologist Frans Vera who championed a controversial rewilding project on reclaimed land near Amsterdam, the Oostvaardersplassen. There are other large projects across the continent, but none in England apart from Knepp. Vera dismissed conventional belief in northern Europe under uniform tree cover before human immigration. He imagined a cool savannah with indigenous red deer, wild boar, extinct aurochs and other large herbivores grazing in a mosaic of forest and grassland. Without a tightly-knit canopy it was a more biologically diverse and productive environment.

Knepp estate
Fallow deer

Strictly speaking, Knepp is not rewilded, which is why her book is titled, ‘Wilding’. Regulations, public opinion and feasibility forbade reintroduction of some native fauna. There could be no brown bear, wolf, lynx and of course auroch that might escape into local gardens, and even wild boar and beavers were excluded, though some feral animals already lurk in the English countryside. The environmental entrepreneurs had to find mimics for the original inhabitants: ancient breeds of cattle (English longhorn) and pigs (Tamworth) and they introduced fallow deer. Wildflower seeds were broadcast and Victorian drains were removed to recreate wetland, which would have horrified ancestors. Nature claimed land back rather quickly considering how long heavy hands ruled there. Herds of herbivores became self-sustaining, so much so they had to be controlled by harvesting or transfer to other estates.

Knepp estate
Tamworth pig and Longhorn cattle

Vera predicted browsing herbivores and the shovel noses of pigs would reshape the landscape. Animals and plants that were rare or extinct returned in remarkable numbers, many for breeding, including nightingales, purple emperor butterflies and two of the rarest bats.

Even the more pigheaded detractors have admitted the couple’s courage and fortitude. Government grants were beyond reach, even from agencies founded to promote nature, and the whims of nature offered numerous obstacles and setbacks, but support was won from leading naturalists and ecologists who continue to help the project evolve. The estate is now a place of pilgrimage, safari tours and so-called glamping (glamorous camping). The prime organic meat is in demand and helps to provide economic stability that once seemed a dream.

A large estate with a castle isn’t an ideal model for other farms with marginal land and strained budgets, but Knepp is shining example for them to consider formerly unthinkable options that frighten bank managers. There is no more conservative base than the countryside where people will often resist change by appealing to aesthetics. But the beauty of landscape is in the eye of the beholder and the image of fields clothed in monoculture and hills (called downs) cropped to the dirt by fluffy sheep has changed, and quite perceptively even in my memory from intensive farming. This is a matter of Shifting Baselines, described in a much earlier post. The southern English countryside is more bereft of wildlife and open spaces for spiritual refreshment of local and visiting folk than any European neighbor. It lost wilderness thousands of years ago to cultivation of almost every fertile acre.

Young people were always a source of hope for a brighter future and more daring imagination. There are many more today who want to reset our relationship with nature, shifting from the absolute domination of enslaved land to a gentler and more sustainable partnership. Some people ask if this moment of history in a pandemic is an opportunity not to be missed. It is a work in progress, like the Knepp project, and to that I say, Amen.

Photos courtesy of Knepp estate

Death of a Lawn Mower

The novelist F. Scott Fitzgerald knew that Americans find public expression of their successful lives in a neatly groomed lawn. Jay Gatsby was so horrified at Nick Carroway’s ragged lawn next door that he sent his gardeners over to mow the offending sward. As the nation was more prosperous by the 1920s and homes were set back from the road, owners mimicked the greens of Mount Vernon, Monticello and the great estates of 17th and 18th century Britain and France. Inventions of mechanical and powered mowers to replace laborious scything offered much encouragement.

A lawn is an expensive investment, but realtors know the kerbside appeal of perfectly manicured grass helps house sales. It is a sine qua non for the modern suburbanite. Impressions of something familiar we grow up with are hard to budge, and when lost we feel bereft, but if we can step back mentally, it may be seen in new light. When I look at a ‘perfect’ lawn now my mind toggles between lawn and desert (call it cognitive dissonance if you like).

Looks more like a barren landscape on second thoughts

Why desert? Because among nuanced meanings lawns and golf courses are desolate and barren landscapes. If anything tries to nestle in a monoculture of non-native grass it is quickly doused in herbicides and pesticides, which gardeners use even more profligately than farmers. We fight frantically to conquer every weed and bug. Striving for perfection is a virtue better reserved for indoors because outside nature hates uniformity and tidiness.

Nick Carroway is more my kind of guy than his rich neighbor, although I came round lately. I am letting my lawn grow long and wild, like my hair and coronabeard. You might wonder if they are all reactions to the current contagion, yet I argue it is mindfulness and not just a lazy mower.

I love to watch knee-high stems swaying in a breeze. The sward is too dense for weeds to anchor, except the pretty polkadots of white clover and a few wildflowers on the lawn. Did I say lawn? I can now call it meadow. Deer and cottontail rabbits feed and fertilize; butterflies dance by day and lightning bugs cruise at night; goldfinches cram on seed heads; our dogs love to romp and nuzzle there. And, so, besides aesthetics and entertainment value, new and more abundant life sprouts from the death of lawn.

Ben approves of the lawn transition

It is no longer a source of noise and atmospheric pollution (gasoline mowers produce 10x more per hour than a new car). Clover is a bugbear of lawnists, but the virtuous plant boosts soil nitrogen and protects the crust in drought. Without a sprinkler system no water is wasted (more an issue in the West). Overseeding is natural and spontaneous instead of broadcast by hand from a packet, and better quality because the seeds originated from parents that thrive by natural selection. There are obvious savings from lawn chemicals, and precious time is captured from edging, raking and aerating. No more is surplus phosphate drained into streams that open into the Chesapeake Bay.

Lawns only feed pride, yet their collective acreage exceeds that of any food crop in America. What a terrible waste of resource! There is still no shame cultivating a chemical lawn (not yet!), and some homeowner associations and local authorities levy outrageous penalties when people neglect their front lawn, like the retired Florida man threatened with foreclosure when he didn’t pay fines. Lest my readers worry the lawn police will turn up on my doorstep my experiment is neither overlooked by neighbors nor is it kerbside. But I still need to observe politics at home.

There is another reckoning, however, when land is left fallow, and mine will arrive later in the summer with the scorching Virginia sun. That is the time to mow, and not a light task even with a lean and keen Austrian scythe. But it will be a day for looking back with satisfaction and enjoying a rare kind of pride by mowing as our ancestors did in the great estates of yore. 

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