According to some Christian outlooks we were made for another world. Perhaps, rather, we were made for this world to recreate, reclaim, redeem, and renew unto God's future aspiration by the power of His Spirit. - R.E. Slater
Secularization theory has been massively falsified. We don't live in an age of secularity. We live in an age of explosive, pervasive religiosity... an age of religious pluralism. - Peter L. Berger
Exploring the edge of life and faith in a post-everything world. - Todd Littleton
I don't need another reason to believe, your love is all around for me to see. – anon
Thou art our need; and in giving us more of thyself thou givest us all. - Khalil Gibran, Prayer XXIII
Be careful what you pretend to be. You become what you pretend to be. - Kurt Vonnegut
Religious beliefs, far from being primary, are often shaped and adjusted by our social goals. - Jim Forest
People, even more than things, need to be restored, renewed, revived, reclaimed, and redeemed; never throw out anyone. – anon
Certainly God's love has made fools of us all. - R.E. Slater
An apocalyptic Christian faith doesn't wait for Jesus to come, but for Jesus to become in our midst. - R.E. Slater
Christian belief in God begins with the cross and resurrection of Jesus, not with rational apologetics. - Eberhard Jüngel, Jürgen Moltmann
Our knowledge of God is through the 'I-Thou' encounter, not in finding God at the end of a syllogism or argument. There is a grave danger in any Christian treatment of God as an object. The God of Jesus Christ and Scripture is irreducibly subject and never made as an object, a force, a power, or a principle that can be manipulated. - Emil Brunner
Ehyeh Asher Ehyeh means "I will be that who I have yet to become." - God (Ex 3.14)
Our job is to love others without stopping to inquire whether or not they are worthy. - Thomas Merton
The church is God's world-changing social experiment of bringing unlikes and differents to the Eucharist/Communion table to share life with one another as a new kind of family. When this happens we show to the world what love, justice, peace, reconciliation, and life together is designed by God to be. The church is God's show-and-tell for the world to see how God wants us to live as a blended, global, polypluralistic family united with one will, by one Lord, and baptized by one Spirit. – anon
The cross that is planted at the heart of the history of the world cannot be uprooted. - Jacques Ellul
The Unity in whose loving presence the universe unfolds is inside each person as a call to welcome the stranger, protect animals and the earth, respect the dignity of each person, think new thoughts, and help bring about ecological civilizations. - John Cobb & Farhan A. Shah
If you board the wrong train it is of no use running along the corridors of the train in the other direction. - Dietrich Bonhoeffer
God's justice is restorative rather than punitive; His discipline is merciful rather than punishing; His power is made perfect in weakness; and His grace is sufficient for all. – anon
Our little [biblical] systems have their day; they have their day and cease to be. They are but broken lights of Thee, and Thou, O God art more than they. - Alfred Lord Tennyson
We can’t control God; God is uncontrollable. God can’t control us; God’s love is uncontrolling! - Thomas Jay Oord
Life in perspective but always in process... as we are relational beings in process to one another so life events are in process in relation to each event... as God is to Self, is to world, is to us... like Father, like sons and daughters, like events... life in process yet always in perspective. - R.E. Slater

Tuesday, December 16, 2014

Biologos - Adam, Eve, and Human Population Genetics, Part 2: A premier on population genetics

Adam, Eve, and Human Population Genetics
Part 2 -
A premier on population genetics

In this series, we explore the genetic evidence that indicates humans became a separate
species as a substantial population, rather than descending uniquely from an ancestral pair.

by Dennis Venema
December 10, 2014

Evolution as gradual change at the population level

One of the most common misunderstandings about evolution is failing to appreciate that evolution happens topopulations, not individuals. But, you might interject, populations are made up of individuals – so how does that work? The answer is that yes, genetic variation enters a population through mutations in individuals – but that only when such variation accumulates within a population and shifts its average characteristics do we observe its effects.

Perhaps an analogy will help here – one that I have used before, that of language change over time. Languages are like populations – they have a large number of individuals who speak it. While each individual has their own particular quirks (favorite phrases, word preferences, and perhaps even chronic spelling mistakes) any one person cannot, on the whole, cause significant change to their language within their lifetimes. Additionally, any person who does change radically from their language group will effectively be placing themselves outside it – if their changes are large enough to hinder their intelligibility to others. So, language evolution is not an individual affair. Yet languages do change over time, and individuals do contribute to that change. Someone might invent a new word that catches on, for example. Others might be part of the “catching on” – hearing a new word, or new phrase, and repeating it to others. Over time (perhaps generations) a language will slowly adopt new words, new spellings, and new rules of grammar (such as split infinitives in English – to boldly split what no man has split before – but I digress). Yet, such adoptions are gradual. They enter the language as rarities, slowly become more common, and eventually become the “normal” way of doing things (much to the chagrin of English teachers). Thankfully, such changes typically take longer than one generation, sparing those of us who cringe at the novelties of our day. If the English words “there, their and they’re” ever officially collapse into one word determined solely by context or the use of apostrophes to form plurals becomes standard, I’m thankful I won’t be here to see it.

Just as a language has many speakers, a species has many members. They must be genetically compatible – i.e. speak the same language – but they are not all genetically identical – they have their own particular variation within an acceptable range to be in the group. In other words, though populations are a unit (they interbreed) they have genetic variation.

In the terminology of genetics we can understand this in terms of genes and alleles. While all members of the population have the same genes, they do not all have exactly the same version of any given gene. Different versions of a gene are called alleles, and they arise through mutations – that is, copying errors when chromosomes are replicated. For humans, we may have up to two different alleles for any gene – the allele we inherit from our mother, and the allele we inherit from our father. If have two different alleles, we are said to beheterozygous for that particular gene. If we have two identical alleles for a gene, we are homozygous for that gene. While any individual can have up to only two alleles, populations as a whole can have hundreds or even thousands of alleles.

In any given generation, the vast majority of the alleles present in a population were inherited from the previous generation – just like a language group learning from their parents, and picking up the language as a whole, but also some of their particular linguistic quirks. Each generation also can contribute its own novelty to the population in the form of new alleles arising through mutation – just like teenagers coming up with new words or phrases. These new alleles, are rare of course – they are only held by one individual at the beginning. Over many, many generations, however, such new alleles can become more common within a population if they are passed down, progressively, to more and more offspring. In time, the new allele might become the most common one within a population. Many generations later, it might be the only allele present for that gene in the entire population. Combined with the actions of other new alleles of many other genes, over time the average characteristics of the population can change. While it’s challenging to imagine this for genes and alleles, it’s simple to illustrate with language – for example, the change we see in linguistic trajectory towards present-day English in a verse from John’s gospel:

John 1:29, West Saxon Gospels, c. 990

Anothir day Joon say Jhesu comynge to hym, and he seide, Lo! the lomb of God; lo! he that doith awei the synnes of the world. (Wycliffe Bible, 1395)

The nexte daye Iohn sawe Iesus commyge vnto him and sayde: beholde the lambe of God which taketh awaye the synne of the worlde. (Tyndale New Testament, 1525)

The next day Iohn seeth Iesus coming vnto him, and saith, Behold the Lambe of God, which taketh away the sinne of the world. (KJV, 1611)

The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world. (KJV, Cambridge Edition)

The next day John saw Jesus coming toward him and said, “Look, the Lamb of God, who takes away the sin of the world!” (NIV, 2011)

Note well that these “forms”, as we see them here, themselves have many gradations between them, of course. These selections are useful for our illustrative purposes, however. Note that the overall shift to the “modern” text is the cumulative result of many individual changes. To return to our analogy, if every word is a gene, we see shifts in alleles over time as follows:

cwæð → seide → sayde → saith → said

synne → synnes → synne → sinne → sin

to hym cumende → comynge to hym → commyge vnto him → coming vnto him → coming unto him

Though the changes in each word contribute to the overall transformation, each word has only a relatively minor effect on its own. Yet the combined actions of changes in many words, over time, can change West Saxon to modern English. There are not, however, large jumps at any point along the way – each generation of speakers could easily understand their parents and their children – but over time, the shifts are large enough that West Saxon and present-day English are not even close to being the same language.

In the next post in this series, we’ll consider how changes in alleles can lead to new species – much like change over time can lead to new languages.

For further reading:


Dennis Venema is professor of biology at Trinity Western University in Langley, British Columbia. He holds a B.Sc. (with Honors) from the University of British Columbia (1996), and received his Ph.D. from the University of British Columbia in 2003. His research is focused on the genetics of pattern formation and signaling using the common fruit fly Drosophila melanogaster as a model organism. Dennis is a gifted thinker and writer on matters of science and faith, but also an award-winning biology teacher—he won the 2008 College Biology Teaching Award from the National Association of Biology Teachers. He and his family enjoy numerous outdoor activities that the Canadian Pacific coast region has to offer. Dennis writes regularly for the BioLogos Forum about the biological evidence for evolution.

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