Explaining this is tricky. Previously, some had speculated that the strange distributions of creatures such as the white-lipped grove snails could be explained by convergent evolution—in which two populations evolve the same trait by coincidence—but the underlying genetic similarities between the two groups rules that out. Alternately, some scientists had suggested that the white-lipped variety had simply spread over the whole continent, then been wiped out everywhere besides Ireland and the Pyrenees, but the researchers say their sampling and subsequent DNA analysis eliminate that possibility too. “If the snails naturally colonized Ireland, you would expect to find some of the same genetic type in other areas of Europe, especially Britain. We just don’t find them,” Davidson, the lead author, said in a press statement.
Moreover, if they’d gradually spread across the continent, there would be some genetic variation within the white-lipped type, because evolution would introduce variety over the thousands of years it would have taken them to spread from the Pyrenees to Ireland. That variation doesn’t exist, at least in the genes sampled. This means that rather than the organism gradually expanding its range, large populations instead were somehow moved en mass to the other location within the space of a few dozen generations, ensuring a lack of genetic variety.
“There is a very clear pattern, which is difficult to explain except by involving humans,” Davidson said. Humans, after all, colonized Ireland roughly 9,000 years ago, and the oldest fossil evidence of grove snails in Ireland dates to roughly the same era. Additionally, there is archaeological evidence of early sea trade between the ancient peoples of Spain and Ireland via the Atlantic and even evidence that humans routinely ate these types of snails before the advent of agriculture, as their burnt shells have been found in Stone Age trash heaps.
The simplest explanation, then? Boats. These snails may have inadvertently traveled on the floor of the small, coast-hugging skiffs these early humans used for travel, or they may have been intentionally carried to Ireland by the seafarers as a food source. “The highways of the past were rivers and the ocean–as the river that flanks the Pyrenees was an ancient trade route to the Atlantic, what we’re actually seeing might be the long lasting legacy of snails that hitched a ride…as humans travelled from the South of France to Ireland 8,000 years ago,” Davidson said.
All of the following evidence supports the passage’s explanation of sea travel/trade EXCEPT:
- archaeological evidence of early sea trade between the ancient peoples of Spain and Ireland via the Atlantic Ocean.
- the oldest fossil evidence of white-lipped grove snails in Ireland dates back to roughly 9,000 years ago, the time when humans colonised Ireland.
- absence of genetic variation within the white-lipped grove snails of Ireland and the Pyrenees, whose genes were sampled.
- the coincidental existence of similar traits in the white-lipped grove snails of Ireland and the Pyrenees because of convergent evolution.
The Correct Option is D
Solution and Explanation
The correct answer is ():
The idea of convergent evolution would weaken the author’s argument of sea travel or trade. The author’s argument is that convergent evolution can be ruled out on the basis of the underlying genetic similarities between the two groups. If the author has ruled out convergent evolution, then it cannot be used as an evidence of the snails’ sea travel. The sea travel has been used as an evidence in support of the purported snails’ migration by sea from Spain to Ireland.
In paragraph 4, the evidence that “humans routinely ate these types of snails before the advent of agriculture” can be used to conclude that:
- 9,000 years ago, during the Stone Age, humans traveled from the South of France to Ireland via the Atlantic Ocean.
- white-lipped grove snails may have inadvertently traveled from the Pyrenees to Ireland on the floor of the small, coast-hugging skiffs that early seafarers used for travel.
- the seafarers who traveled from the Pyrenees to Ireland might have carried white-lipped grove snails with them as edibles.
- rivers and oceans in the Stone Age facilitated trade in white-lipped grove snails.
The Correct Option is C
Solution and Explanation
The correct answer is (C):
To answer this question, we must carefully understand the main idea of the passage. The passage is about white-lipped grove snails which are found only in Spain and Ireland. The passage focuses on why they are found only in these two places. The author seems to have ruled out a no of possibilities and has zeroed down on the migration theory, through which he suggests that the snails might have migrated on the ships or boats of seafarers who might have carried them as eatables. If humans routinely ate these types of snails before the advent of agriculture, then we can conclude statement 3 which says that seafarers might have carried white-lipped grove snails with them as edibles.
Which one of the following makes the author eliminate convergent evolution as a probable explanation for why white-lipped grove snails are found in Ireland and the Pyrenees?
- The absence of genetic similarities between white-lipped grove snails of Ireland and snails from other parts of Europe, especially Britain.
- The distinct lineage of white-lipped grove snails found specifically in Ireland and the Pyrenees.
- The absence of genetic variation between white-lipped grove snails of Ireland and the Pyrenees.
- The coincidental evolution of similar traits (white-lipped shell) in the grove snails of Ireland and the Pyrenees.
The Correct Option is C
Solution and Explanation
The correct answer is (C):
This point has come in the passage. The idea of convergent evolution has been eliminated by the author because there are genetic similarities between the two groups found in two different countries. Presence of genetic similarities means absence of genetic variation. Thus option 3 is the best choice. Option 1 is just the opposite. Absence of genetic similarities would support convergent evolution.
The passage outlines several hypotheses and evidence related to white-lipped grove snails to arrive at the most convincing explanation for:
- how the white-lipped variety of grove snails independently evolved in Ireland and the Pyrenees.
- how the white-lipped variety of grove snails might have migrated from the Pyrenees to Ireland.
- why the white-lipped variety of grove snails are found only in Ireland and the Pyrenees.
- why the white-lipped variety of grove snails were wiped out everywhere except in Ireland and the Pyrenees.
The Correct Option is C
Solution and Explanation
The correct answer is (C):
We have to understand the question to arrive at the right answer. The question speaks about several hypotheses. On the basis of ‘several hypotheses’ and ‘the central idea of the passage’, we can shortlist two choices. The central idea is about why the white-lipped grove snails are found only in two places. The wiped out idea in option 4 is nowhere mentioned in the passage. So we can eliminate choice 4. Since there is no independent evolution of the two, we cannot choose option 1. We must not forget that convergent evolution and independent evolution are one and the same thing.
We are left with two choices only. The first is why the white-lipped grove snails are found only in these two places, and the second is how they might have migrated. The migration theory is a tempting choice, but there are not several hypotheses for this. There is only one hypothesis for the migration theory: the snails might have travelled on boats of seafarers, who might have carried them as eatables.
But there are several hypotheses, some rejected while some improbable, why the snails are found only in these two places. In fact, the whole passage seems to be discussing this idea only. Thus, choice 3 is the best answer.
Top Questions on Reading Comprehension
Passage: Toru Dutt is considered the earliest Indian female writer in English. She travelled extensively in Europe from a young age with her family. She and her sister Aru became fascinated with Paris and French literature. In London, they came in contact with such august personages such as Sir Bartle Frere, the Gover- nor of Bombay from 1862 to 1867, and Sir Edward Ryan, the Chief Justice of the Supreme Court, Calcutta, from 1837 to 1843. Toru Dutt was greatly influenced in her writings by French Romantic poets like Victor Hugo and English writers like Elizabeth Browning, John Keats, Charlotte Bronte and Jane Austen. She was also intrigued by the legends and myths of India, and even learned Sanskrit. Her writings were marked by romantic melancholia and an obsession and preoccupation with death. This was partly due to her suffering and pain following the early tragic deaths of her siblings, especially her older sister Aru, with whom she was quite close. Her chosen subjects often portrayed separation, loneliness, captivity, dejec- tion, declining seasons and untimely death. She led an ”Ivory Tower existence” and her own death came quite early, at the age of 21, in the full bloom of her talent and on the eve of the awakening of her genius. Toru Dutt’s most famous work is A Sheaf Gleaned in French Fields, an anthology of poems translated from French to English. It also contained a few original poems that showcase her vast insight into French literature. She used to publish poems in the Bengal Magazine, under the pseudonym ”TD”. But most of her powerful work was published posthumously, in- cluding the French novel Le Journal de Mademoiselle D’Arvers and the unfinished English novel Bianca, or, the Young Spanish Maiden. Her work Ancient Ballads and Legends of Hindustan depicts a shrewd knowledge of Hindu mythology and an instinctive empathy with the conditions of life they represent. An assimilation of the Occident and the Orient nourished Toru’s poetic skills; in her, we find a tripartite influence of a French education, lectures at Cambridge and the study of Sanskrit literature.
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“Why do they pull down and do away with crooked streets, I wonder, which are my delight, and hurt no man living? Every day the wealthier nations are pulling down one or another in their capitals and their great towns: they do not know why they do it; neither do I. It ought to be enough, surely, to drive the great broad ways which commerce needs and which are the life-channels of a modern city, without destroying all history and all the humanity in between: the islands of the past.”
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“Why do they pull down and do away with crooked streets, I wonder, which are my delight, and hurt no man living? Every day the wealthier nations are pulling down one or another in their capitals and their great towns: they do not know why they do it; neither do I. It ought to be enough, surely, to drive the great broad ways which commerce needs and which are the life-channels of a modern city, without destroying all history and all the humanity in between: the islands of the past.” (From Hilaire Belloc’s “The Crooked Streets”)
Based only on the information provided in the above passage, which one of the following statements is true?
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THE FAIR ISLE METHOD: Fair Isle knitting is a traditional technique that involves using two or more colours of yarn in a single row to create intricate patterns and designs. This method requires careful tension management to ensure even stitches and prevent puckering. To begin, select your colours and cast on the desired number of stitches. As you knit, alternate between colours every few stitches, carrying the unused yarn along the back of the work. Mastering the Fair Isle technique allows you to create stunning visual effects in garments, accessories, and home textiles.
THE CONTINENTAL STYLE: The Continental knitting style, often referred to as “picking,” involves holding the yarn in the left hand while the right hand manipulates the needles. This method allows for greater speed and efficiency, particularly when working with complex patterns or multiple colours. To practice this style, start by casting on your stitches and using your left hand to tension the yarn. With each stitch, simply “pick” the yarn with your right needle, forming a quick and fluid motion. As you become comfortable with this technique, you may find that your overall knitting speed and comfort improve significantly.
THE SHORT-ROW TECHNIQUE: Short-row knitting is an advanced technique that allows for the creation of shaped garments, such as sleeves and shoulders, without the need for complex shaping. To make a sleeve using this technique, begin by casting on the required number of stitches. Work a portion of the row, then turn your work and return without completing the full row to create the “short rows” that shape the curves of the sleeve. To prevent holes at the turn, wrap the stitch before you turn your work. Repeat this process as needed to achieve the desired shaping and dimension of the sleeve. Once you have shaped the sleeve, you can then sew the side seams to connect the pieces of your garment and finally, complete the edges to ensure a clean finish. This method not only helps shape curves but also adds dimension to your piece, allowing you to enhance fit and style.- AILET BALLB (Hons.) - 2025
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