Sunday 30 April 2017

Garden Myths by Robert Pavlis

Blogger and myth buster extraordinaire 

The mists will fall from the eyes of many gardeners when they read about 120  gardening misconceptions in Robert’s new book. With razor sharp focus he exposes lies, misunderstandings, wrong explanations, erroneous assumptions and stuff that’s just plain wrong. He finds myths I never knew existed!
He is a trained chemist and lifelong gardener. His diverse horticultural interests are illuminated by his other two fine books on orchids and ponds. (I personally learned from his blog the significance of an orchid’s velamin root cover to its watering and was delighted to read someone else saying ponds do not have to have filters and pumps and other paraphernalia)
He is totally fearless in condemning hyped up useless products and snake oil selling. Just like his blog the book references and links all his sources. He shows great ingenuity in devising simple experiments that expose common fallacies. It’s all done with a wry sense of humour. 

He attempts to distil sound gardening advice from his myths and recommends good garden practice in rounded discussion. He mostly succeeds but it is awfully difficult when giving advice not to create myths of your own!

It is not surprising that I admire Robert Pavlis. He shares much of my own gardening philosophy and stubborn foibles. It is music to my ears to read support for almost all my own thoughts on the benefits of minimum cultivation. It would seem that his naturalistic approach is sometimes even more extreme than my own and I wonder if his six acre garden is as scruffy as mine. (Like me he directly recycles most of his organic matter). Like me he has no fundamental objection to gardening chemicals but in most cases finds no need to use them. He never talks about glyphosate. Now there is a difference!  
(Since writing this post he has mounted a stern defence on his blog for the safety and utility of glyphosate. To me popular fears about this chemical that has been used safely for more than fifty years is the greatest myth of all)

It is an almost impossible task to write a perfect book about gardening myths. Their is such a difference between the gardening knowledge of readers. They range between weekend - or even bank holiday - gardeners with little plant knowledge or scientific interest and those who like me are complete gardening nerds. I think to provide adequate rebuttal of those myths that are merely simple delusions or misconceptions is so very different to discussing more sophisticated and widespread beliefs. Mr Pavlis bridges the gap rather well.

I know (hope) that Robert would like me to discuss some of the myths he has raised. I cannot resist the opportunity. 
You will find we have differences of styles, opinions and gardening philosophies but complete agreement on actual facts

We disagree on definition as I discussed here. Language between North America and ourselves can be a barrier as well as a union. We do seem to agree that there are many gardening circumstances where fertilisers are not needed at all. We are both suspicious  of do-it-yourself soil analysis and are both keen to advice gardeners to bring local observation to the fore when making decisions on plant nutrition.
We disagree whether professional soil analysis is ever worthwhile to the amateur. Robert wants to correct any nutrient deficiency precisely. I prefer a generalist approach and use my general yaramila fertiliser - er generally - and let the plant take up the nutrients it needs. I would find it impossible to translate a complete professional soil analysis for the very diverse needs of the plants that I grow.
Robert publishes a very interesting list of plant nutrient deficiency symptoms. We both agree that in the real gardening world they are of limited value.

The mystery of the sinking soil
Apparently our friends over the water have garden soil that sinks! I do not recognise this as a problem over here. It is explained in terms of added organic matter decaying - as it certainly does! (And we both agree why - not least as a result of excessive soil stirring).
I do hate sunken borders where the innocent new gardener excavates out his weedy soil and bins it!  (Any one dumping good soil in a wheelie bin ought to be horse whipped - but perhaps that is a myth).
My own experience is that borders rise - perhaps in my own case casting worms remove soil from my lawn. I remember at horticultural college the student plots after several years needed to be lowered. They were of course very heavily manured and new planting had attached soil and all end of season debris was dug in.
I remember years ago a former student gave us a lecture about his landscaping experience in America. We were horrified how a new site was completely stripped of all vegetation and soil! Surely they still do not do that now?
It does seem that American gardeners frequently cover their soil with a substance called triple mix. It is a mixture of third parts peat, soil and garden compost. Do they throw all their old soil and organic matter away? We know that organic matter is lost to decay but not soil’s sand, silt and clay.
I know that Robert is very hot on recycling his own organic matter. I bet he personally does not need to import topsoil. 
In my view it is a myth that organic matter needs to be imported to maintain soil fertility. You can grow it yourself.

Spring bulbs

Robert Pavlis would approve that these bulbs have been reappearing for more than ten years

I initially thought that Robert was scraping the barrel about some gardener’s false belief that Spring bulbs such as daffodils, hyacinths and tulips are better lifted after flowering and should only be planted after first frost. The latter being both particularly stupid and unlikely! The earlier Spring bulbs are planted in late Summer/Autumn the better!
On further thinking one can understand how the first myth might have developed. In traditional Spring bedding, borders are replanted for Summer. It is convenient (but bad practice?) to get the bulbs out of the way. Lifting bulbs before they die down is particularly damaging and their quality is hugely diminished. 

Keukenhof garden 
Last year we visited the famous Dutch garden at Keukenhof. where they plant fifteen million bulbs every year. After flowering they are lifted and thrown away. No wonder some gardeners think that bulbs should be lifted! Robert and I prefer to leave them in the ground for ever.

I expect some of these were even upside down

When I planted 8000 bulbs for Lyndi last Autumn I was glad I already knew that It did not matter a jot whether they were upright or at what depth they were planted. You will see from his book that Pavlis agrees.

Myths or just lack of knowledge?
Robert observes that many gardeners think that fungus diseases - take powdery mildew as an example - are all the same. It is important to realise that they are not and that for example apple powdery mildew is not the same powdery mildew that spoils michaelmas daisies. This is important but does it count as a myth?

Language divides us

A very strange herb.  Our guide gave us several ‘facts’ about its life cycle - mainly wrong
I remember when Monty Don confused the nation when he declared bananas were herbs. I was amused that our recent tour guide in Maderia said the same thing when we visited a banana farm. Fellow punters listened with wide eyed innocence and filed the ‘fact’ away in their minds.
This nonsense stems from the word having two meanings. In as much as a banana is a herbaceous plant it is a herb. However to most of us  herbs are such as mint (a herbaceous perennial), sage (a shrub), thyme (a sub shrub) and parsley (a biennial).
I may be pedantic but Robert’s #myth 64 ‘Lavender and Russian sage are perennials’ is wrong!  I hope you can get your head round the double negative - the statement is true and it is not a myth - they are perennials - at least on this side of the pond! 
To make me happy it only makes sense if the word ‘herbaceous’  precedes ‘perennial’. Then I agree that the sub shrubs - the woody perennials that Robert writes about makes a very valuable point.
I was intrigued with his suggestion that you can regenerate gnarled old lavender by earthing up and new rooted plants can be later detached and planted.
I thought this practice was one of my own foibles! I call a modified version ‘piggy back planting’. I dig out the old sub shrub and immediately replant it very deeply with only the tips showing. The old root eventually dies but the rooted tops carry on to make a new plant. It works with some other plants too.

Rejuvenating Dianthus 'Doris’

I know my soil is acid and that carnations like lime. I have no idea if this dolomitic limestone will do any good!

Job done

Final thoughts
Under the cover of myths Robert has written a very fine book on to how to successfully grow plants and cut out the nonsense. You need to read carefully his rounded discussion. Not all myths are as clear-cut wrong as they seem and there are sometimes exceptions.

Robert’s defence of glyphosate

Wednesday 19 April 2017

Malus x purpurea ‘Crimson Cascade’. Chelsea launch

Alan Warwick’s garden secret. Will it be a Chelsea Sensation?

Alan's tree (before the propagators called)
Alan swore me to secrecy. He had raised a brand new weeping ornamental apple tree and that ‘in a few years’ it would be launched by Hilliers at Chelsea. This is the year!

My readers already know eighty seven year old industrial chemist Alan Warwick! Former ICI boffin, he is my former student (a mature one) who when on the gardening course at Askham Bryan declared that in scientific terms the standard botanical explanation of how water gets to the top of a tall tree is complete nonsense! I don’t know if he is right but he offers his own explanation. I wrote about it last year.

Every gardener knows that it is completely stupid to try to propagate an apple by sowing a pip. Not only will a new seedling take more than a decade to fruiting, the odds are phenomenal against it being worth eating. In this case flowering.

Alan knows this but his scientific curiosity got the better of him and fifteen years ago he collected a few pips from his ornamental apple tree and raised a dozen seedlings. A few had the dark green leaves of its parent Malus aldenhamensis and he gave some away. He kept one that looked a little bit different and which after a few years clearly showed a pendulous habit. It would be years before it produced its magnificent crimson flowers. Of course anyone buying a grafted plant from Hilliers will have a flowering plant next year!

In 2014 Alan sent Hilliers a photograph. They were on the line straight away and were up in York the very next day. Alan’s weeping apple is sensational. It fills a gap in a gardener’s repertoire. There is no other weeping apple that shares its neat compact elegant nature and its fantastic dark crimson flowers. It is destined for greatness. Hillier have no doubt raised nye on a thousand. In a decade I suspect that around the world there might be nearer a million.

After the grafters descended
At propagation time Hillier’s propagators decimated his tree to collect grafting material. It has now recovered its strong weeping habit. It is a tribute to their skill that soon in 2017 plants will be on the market. Alan’s tree is of course on its own roots. The grafted plants will be just as good or even better. I predict it is going to be a garden phenomenon when it is launched at Chelsea this year'

Now starting to recover from mutilation
The tree
It is a dead ringer for its magnificent parent Malus aldenhamensis - except for its superb pendulous and compact habit. It makes no more than fifteen foot high. The dense flowers are a vibrant crimson, the foliage is a fetching reddy bronze and its small long lasting dark red  autumn crab apples feed the birds.

Lovely red foliage
The ‘mother’ of Alan’s weeper
Its mother, Malus aldenhamensis is described as ‘spreading’. ‘Crimson Cascade’ is much better and actually weeps. Quite strongly, but fortunately not so tightly as to make a tight dome sweeping the ground. It is the perfect weeper not too spreading not too dense.

Some weeping plants can be downright ugly
Like it’s parent Crimson Cascade has a strong  constitution and unlike similar weepers such as peach and cherry it harbours only minor pest or disease. It is bone hardy and has twice experienced minus twenty centigrade for prolonged periods and not turned a hair. Alan tells me his tree has been flooded twice yet still thrives!

Malus aldenhamensis in Bolton Percy churchyard
The naming of Malus x purpurea ‘Crimson Cascade’
Alan wanted to call it ‘Jean Warwick’ as a tribute his late wife. The ‘suits’ said “no, that won’t sell”. (This tree would sell if you called it a pig in a poke). They came up with ‘Crimson Cascade’ a very fine name. Pity there is a weeping peach with the identical moniker!

I had the same experience when helping Yorkshire author Joyce Fussy when she registered her wonderful white dicentra which was similarly launched at Chelsea - thirty years ago. I wanted to call it ‘Joyce Fussey’. Instead it was to be ‘Avalanche’. What a very fine name. On its launch at Chelsea it had turned up as  ‘Snowflakes’. I am sure you can guess why.

Some of the best plants I know are named after real people. I don’t agree with the nurserymen especially when a name has an evocative story.

The nerds among you will have noticed the x in the ‘latin name’ indicates hybrid origin - x purpurea means the malus species is a hybrid. In this case not a recent hybrid, ‘Crimson Cascade’ is from a self pollinated flower. It’s mother Malus aldenhamensis itself was a chance seedling found in a garden in Aldenham many years ago. It would be now speculation to discern whether that was the original hybrid cross.

My own ‘aldenhamensis’ has been here thirty years
Hillier's other 2017 Chelsea Introductions

Corydalis ‘Porcelain Blue’

Another hybrid, one that occurred at Hilliers by natural and random insect cross pollination. Ten years observation at Hilliers show it to have strong hybrid vigour and to flower for much of the year. I suspect that it’s parents are Corydalis elata and Corydalis flexuosa. I don’t actually know this but I grow the variety ‘Spinners’ which has the same parents and in my garden has had flowers March through to December. (With short rests in-between). The beautiful porcelain blue in Hilliers' new variety looks the same as that in Corydalis ‘Blue Summit’.
I have soft spot for Corydalis flexuosa and elata and two years ago blogged about their cultivation.

My Corydalis elata makes a much better open ground plant than does Corydalis flexuosa
Lilium formosanum ‘pricei’

Recognition at last!  (The plant I mean). I have grown this delightful dwarf lily for years - and sometimes lost it too. If you save its prolific seed you will have dozens of full size replacements 15 months from sowing. Just imagine a lily a couple of inches high holding full size white lily flowers aloft up to four inches! Some think it strange but I find it delightful and it is one of my favourite plants.

I think my own Lilum formosanum pricei is an extremely dwarf form and the size I quote might mislead you. In common with most available plants of this species Hilliers’ plants grow about 15 - 18 inches high.

They are hoping to achieve their seventy second gold medal at Chelsea this year and have exhibited there for more than a hundred and fifty years.

I have fond memories of regularly thumbing through their catalogue which was our bible at the Lancashire College of Horticulture fifty years ago. If a Lancashire gardener needed us to identify or obtain a tree or shrub it was always from Hilliers Manual. It was a complete list of trees and shrubs available from Hilliers and embraced just about every woody plant grown in the UK. Many botanic gardens were stocked from Hilliers as were many other gardens owned by the great and the good.

The 72 acre Harold Hillier Garden at Romsey was donated to the public and is a must for any gardener visiting the Winchester area.
The Hillier catalogue eventually appeared as a book and is still very well worth buying.

Alan Warwick

Alan’s prize potatoes
Alan is 87 now and is looking good for a hundred. He is delighted to know that his tree will be his legacy to the gardening world. As to his theory of water movement up a tree he recognises the world is not yet ready to believe him. I suspect as a scientist recognition of the latter would give him as great a satisfaction.
They have invited him down to Chelsea. He will be there on Thursday. In my opinion he ought to be there with the celebrities on Monday.

Alan’s own tree burst into Spring growth ten days ago. It has the good sense to come into flower at Chelsea time!
Alan at Chelsea
The dicentra that went to Chelsea
My corydalis post
Alan Warwick's botanical theory
I have been carried away with new pictures from Alan and have posted again!
It's going to be an absolute stunner

Wednesday 12 April 2017

Seaton Ross Open Gardens 2017

Sunday 7th May
Rhododendrons and Magnolias at Weathervane House
The village event on the above date is the occasion when about half a dozen village gardens will be open. 

I am using this notice to also publicise the opening arrangements for myself and Peter Williams at Weathervane House for the whole of the year. We  both have been deemed up to standard  to open on the 7th May. Peter of course has been a constant inspiration to this blog!

Here are the official details of the actual village Open Day

Seaton Ross Open Gardens 2017

Boundary Cottage (a National Gardens Scheme yellow book entry) and Whixley Lodge      
You may need to get in your car to come the half mile out of the village. Boundary Cottage is a  ¾ acre plants man’s garden which includes twin ponds, gravel borders, cactus and succulent plants, herbaceous borders, boggy planting, a rock garden and fruit and vegetables. This garden holds the National Dicentra collection and Roger Brook writes a blog about his garden as nodiggardener. 
Next door is Whixley Lodge - a garden beginning to be restored, visitors are welcome to take a stroll around and to meet the pet Rheas - Phleas and Spike.

  1. Weathervane House (usually a National Gardens Scheme yellow book entry)
This is a two-acre woodland garden with magnolias, rhododendrons, azaleas, flowering trees and shrubs together with mixed herbaceous borders, lawns and a circular meadow.  The woodland areas are at their best in April and May and the herbaceous border looks attractive from early June. There is also a fruit garden, a glasshouse and a large polytunnel with specimen rhododendrons and many other plants propagated on site. Plants are for sale.

  1. Parish Plot and village information board

1The parish plot is owned by the Parish Council for the use of villagers and it has gradually been reclaimed from wild since 2005. Overgrown with ground elder it was treated with weed killer several times and garden plants introduced over the years. It is now a wild garden maintained on the same no-dig principle as Boundary Cottage. 
Once the site of charitable homes for old age village residents, the old fruit trees remain but only foundations of the houses. 

  1. Catton Cottage

This pretty, individual garden demonstrates the gardeners like for quirky features. Irregular shaped beds, wall mirrors and interesting objects nestle among the plants and enhance the flowers.

  1. Swallow Cottage

Small is Beautiful! This tiny garden bursts with life and healthy produce each year. Lean over the wall to see what’s growing; in pots, bags and hangers are five sorts of fruit, eight sorts of vegetables, blooms and produce. It just goes to show what a lot can be done with a small plot. 

  1. Ashlands

This garden has been planted with lower maintenance in mind. There are shrubs such as rhododendrons and roses under planted with spring and summer bulbs and some herbaceous foliage plants such as Hostas and ferns. Part of the garden is heavily shaded by the Norway Maple and Beech trees in the churchyard so trial and error dictates the plants which succeed in the shady areas. There are paths behind the beds to invite a walk around and among the garden rather than just to look out on to it. 

  1. The Telephone Box

The Parish Council is in the process of buying the decommissioned, red Telephone Box outside the Village Hall. The village is thinking about how best to use and enjoy their new asset. Can you help? There is a suggestion box is inside the Telephone Box and all ideas and input are welcomed. The Telephone Box is decorated with handmade flowers and blooms in keeping with the Gardens Open Day theme.
Throughout the village is a fun Flower Pot Character Trail.    
 St Edmund’s Church is open and welcomes visitors. There are flower arrangements to enjoy. 

Also in Seaton Ross: The Pocklington Area Open Studios have three artists displaying their work at Old Mills at the junction of Breckstreet Lane, North End and Mill Lane
Also the Young Farmers Tractor Rally is this weekend and may pass through the village.


If I might add that Cathi my blogmeister has been dragooned into opening and denies any responsibility. Regular readers will know that I personally maintain her garden which is next door to me. 
Cathi’s grass verge outside the garden alongside the road has been a major blog project and is always on view!

Similarly I also maintain the village plot that is always open

Later dates
Later in the year both Peter and I are opening in aid of the Yorkshire Arboretum. If you don’t know TheYorkshire Arboretum at Castle Howard you must go there too - any time during the day! (It’s independent and separate to Castle Howard House)

The arboretum has an excellent Open Garden Scheme where twenty-seven fine gardens, many not always otherwise open can be seen. An all in ticket costs a mere £25 pounds. The best bargain you will find anywhere.
If you want to attend just one garden it will cost you £5.

Peter and myself have a private arrangement for our own two open days whose dates coincide. A £5 ticket will admit you to both our gardens.
On the first occasion on Saturday 20th May 12pm to 5pm refreshments will be only at Weathervane House. On the second occasion on Tuesday 22 August 12pm to 5pm refreshments will only be served at Boundary Cottage.

This is a link to details and dates of the Arboretum scheme

My own yellow book open day at BoundaryCottage under The Open Garden Scheme is on Sunday 10 September 12-5pm and costs £5. Refreshments are available

This is a link to my own details on the Open Garden Scheme  website

Further links
There have been several previous posts about Weathervane House and Boundary Cottage (use the search box). To give you a flavour try Weathervane House and A bit of a do - on the occasion of my wedding! 
This was about the village plot.

Tuesday 4 April 2017

We are hybrids

We are just good friends
When I told Brenda that I was yet again writing about hybridisation she wondered if I was wasting my time and that I was knocking at an open door. Surely it is accepted that hybridity is a significant source and distributer of genetic variation and a driver of evolution?

I was talking to a well informed botanist recently. He said that some botanists thought perhaps a third of all natural plant species were known hybrids. That is amazing. To demonstrate past hybridisation is extremely difficult and as you go back over millions of years genetic evidence becomes vanishingly small. Not to mention geneticists have more rewarding things to do. Perhaps all plants are derived from ancient hybrids? We just don’t have the means to know.

The world’s tallest tree the coast redwood was an ancient hybrid between metasequoia and a sequioadendron

Modest examples of the parent species
A  natural hybrid between two primula species happened at Kew more than a century ago. Initially sterile after several years a flower was able to self pollinate and set seed. It is a common plant now. 

Distinct new plant hybrids have a much easier time than animals to stabilise a new genome. Even if they are infertile, vegetative propagation will often permit their spread and survival; plenty of time and potentially huge numbers  of candidates for fertility to arise.
One successful hybridisation event can produce numerous seeds and plenty of brothers and sisters. Furthermore unlike animals, plants often self pollinate and a new hybrid requires no mate.

Most gardeners know the huge contribution over more than a thousand years of plant breeders crossing distinct species of rose to eventually create those grown today. Less  well known is that Rosa canina is a very complex ancient natural hybrid. Its pollen and female germ cells contribute genetic code unevenly in seed formation and it does not subscribe to Mendelian rules 
Rosa canina is one of the wild ancestors of modern roses. Here it grows wild on the village plot

Animals have it different - but hybridise too
On the BBC ‘earth’ website  Rebecca Ackermann of Cape Town University states that 7-10% of primates have been known to hybridise in nature. That means they have mated and brought forth viable (and often fertile) offspring. Considering their geographical distribution and how few primates overlap this is very revealing  how easy hybridisation can be.
You might well ask what happens to such rare animal hybrids. Their line only continues if they mate with one of their parent species and after a few generations their identity is lost. Never-the-less novel genetic information has moved across so called species barriers. It’s called introgression.

What is really interesting is when the results of any new hybrid crosses becomes geographically isolated and inbreed within a small community leading to new species.

The Appalachian butterfly is a known hybrid and its area of distribution is bordered by the habitat of its original parents

The  power of hybridisation can come from the fact that new genomes are created and genetic code comes together in exciting new combinations.
More mundane  - but perhaps of greater significance  - is the introgression of code of advantageous small mutations - the very stuff of natural selection. There are seven billion of we humans. If a new selective advantageous variation arises on a single occasion (such as the ability to digest lactose or tolerate alcohol)) it has the potential over countless generations to be shared within the complete human race by sexual reproduction. If a new and different mutation occurs elsewhere in the population it is likewise brought into the fold.
This to my mind is a long way from evolution being in straight line when the changes would have taken place in the line of a single organism and the chances of pieces of beneficial new code being shared is billions of times less. (Another way to look at this is that although our ancestry is a straight line all the way back to the first dawn of life this does not hold for the genes)
Sexual reproduction within a species is the way that nature brings together new information - and we even talk about hybridisation between different communities of any said species.

Sexual reproduction across so called species barriers is essentially the same except the potential for novel combination from a much wider gene pool is hugely enhanced.

Evolution has avoided a complete cross species breeding ‘free for all’ by fostering barriers between dissimilar groups.The more genetically similar two species the more likely these evolved prohibitions to successful cross breeding do not apply. The other side of the coin is that crosses between distant cousins are very rare. Never-the-less when distant crosses happen as they surely do, their significance in evolutionary terms is so much the greater.
Species barriers
Enlightened biologists these days question the whole concept of family, genus and species. We retain the facade because it is so useful although cross-species barriers between distinct organisms often resembles a colander.

Wikipedia lists sixty distinct species of epimedium, many newly discovered in China. Word from the plant breeders is that they all seem to be mutually fertile

The so called genetic tree of life is still a useful indicator of of life’s direction. It is not however a straight line and better than the analogy of a tree it would be better to depict it as an infinitely stranded vine constantly dividing and re-binding together.
I still resent black arts such as statistical binning which clean up evidence of horizontal gene transfer every time the tree of life is amended.
Stability of species
Despite genetic code being able to cross species barriers, life’s ability to maintain distinct species is truly amazing and insects found in amber look the same as those today after many million years. Hybridisation can be rare and crosses are ever diluted by back breeding.

Little changed over two million years
The fossil record shows new plant and animal species seemingly appearing  from nowhere and maintaining themselves very little changed over millions of years. Significantly almost identical fossils continue from first appearance either up to extinction or up to the same organism still living today. I once read an imaginative simulation of the nearly two million years that Homo erectus existed. I could not get over the fact that in all that time change was barely perceptible from fossil evidence. 

As I argue today it is only from extraordinary hybridisation events that such stasis is broken and new species arise, including our own. 

Human evolution
The fossil record of 'recent' events
The above text adds to my previous posts that argue for hybridity’s general significance in evolution. Today I now concentrate on the contribution of hybridisation to the human line. I draw on a recent article on the BBC ‘life’ website which adds veracity to my words as an amateur observer. Even more commanding are the links on that website to state of the art genetic investigation.

Neanderthal skull

We shared the planet with neanderthals as recently as 40,000 years ago. ‘Modern neanderthal’ fossils are encountered from back 300,000 years and their emerging line much longer. Blinks of time in evolutionary terms. Even our earliest purported homo ancestors barely clock up ten million years.
There is real genetic evidence that we repeatedly crossed with neanderthals. We contain in our cells up to 4% neanderthal genes. Not only neanderthals but other ‘ancient ‘races such as denisnovans. (Not so ancient as the timescale of our canvas. I love the notion that they were named after Denis - a hermit who had previously lived in the discovery cave!) Some Asian populations have 6% denisnovan genes in their genome
Although none of us go beyond 4% neanderthal they are not all the same genes! It would seem that if all surviving neanderthal genes were brought together we would be 20% neanderthal.
There was a fascinating find in Romania of a 40,000 year old human fossil whose skull showed clear evidence of neanderthal introgression in the jawbone. Known as the Oase individual he had perhaps 9% neanderthal genes and it would seem he was only between four and six generations beyond the actual human x neanderthal hybridisation event. Apparently none of those neanderthal genes are thought to be have passed on into our identity today. 

Going back a very long way

Homo naledi
1500 remarkable skeletons were found in the Rising Star Cave in South Africa 2013 and have been examined worldwide by hundreds of specialists. In 2015 it was named as a new homo species. Not yet accurately dated the skeletons are perhaps a million years old. It is an extreme mixture of archaic and modern human features. Variously described as mosaics or curious mixtures of ancient Austropithicene and modern homo, the word hybridisation seems to be studiously avoided.
It would seem that obscure homo species occurred all over Africa and fossils are now being found all over Asia too. For example you might have read of the dwarf human species Homo floriensis now confirmed not to be a nutritional aberration!
They often describe them as relic populations or evolutionary dead ends. This is true but I cannot  believe they left no contribution.

Fortunately more and more scientists are recognising hybridisation as a very significant part of our own evolutionary history. Many don’t choose to shout it too loudly even when they agree.

I am only too keen to tell the world I evolved from dinosaurs

Final thoughts
If the fate of a new fertile hybrid is to be subsumed into the parent population or survive as a new entity (probably after a few generations of breeding within one of the parent species) then in the latter case there is no time for natural selection into a new niche in the classical way. The new hybrid either lives or dies in finding a new suitable environment. Hybrids are frequently commoner in hostile new challenging conditions.
Humans have evolved with outgoing generalist characteristics that have enabled us to rule the world. We have gone out into the world and exploited myriads of new niches. We are the perfect example of the power of hybridisation.
In old thinking hybrids were aberrant genetic challenges to the natural order. In truth they have always been a principal route to the future

I had just completed this post when Cathi celebrated my three quarter century birthday by giving me the weighty updated version of Richard Dawkins’ wonderful book ‘The Ancestors Tale’. Dawkins is my longtime hero but I have not recently read him. Although always at the forefront of genetic research and the most brilliant exponent of its translation to layman like me I feared he might not embrace modern thinking about hybridisation.
I need not have worried. There would seem to be a subtle sea change in the genetic establishment’s attitude to hybridity. It’s suddenly respectable and although in my opinion the enormity of it’s significance is not yet fully reflected it moves nearer to the insights of that  brave pioneer geneticist Gene McCarthy.


To really learn about evolution this book is required reading

The BBC 'earth' article about human evolution

Eugene McCarthy's website

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