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Top stories The limits of human performance sloth evolution and the magic

first_img(left to right): ISTOCK.COM/PAVEL1964; ISTOCK.COM/SDOMINICK; STEPHAN SCHMITZ/FOLIO ART By Alex FoxJun. 7, 2019 , 3:45 PM Top stories: The limits of human performance, sloth evolution, and the magic finger ratio From elephant-size animals that browsed North American grasslands to moose-size swimmers that plied the Pacific coast of South America, sloths have roamed Earth for more than 50 million years. Yet scientists know little about how the dozens of known species are related to each other. Now, two new analyses of ancient sloth DNA and proteins—some of which are more than 100,000 years old—are rewriting the sloth family tree.Talk to the hand. Scientists try to debunk idea that finger length can reveal personality and healthMore than 1400 papers in just over 20 years have linked the relative lengths of the second and fourth fingers of the hand (known as 2D:4D) to a variety of attributes ranging from intelligence to cancer risk. Researchers who believe in the ratio’s predictive power say it reflects a fetus’s exposure to testosterone and other hormones that guide development, including that of the brain. But the notion has also riled up plenty of critics, who argue that researchers relying on the 2D:4D comparison have been seduced by a simplistic, faulty measure.The transparent teeth of this dragonfish evolved for one lethal purposeFive hundred meters below the ocean’s surface off the coast of California lives a creepy looking sea monster with a huge jaw and sharp rows of teeth. Even creepier, these teeth are transparent. Now, scientists think they know what makes them this way.Researchers strapped video cameras on 16 cats and let them do their thing. Here’s what they foundEver since video cameras became ultraportable, scientists have strapped them onto animals from sheep to sharks to see how they view the world around them. But relatively little has been done with cats, perhaps because they’re so hard to work with. Now, a new study equipped 16 cats with small cameras and followed them for up to 4 years as they prowled their neighborhoods. Click to view the privacy policy. Required fields are indicated by an asterisk (*) Study of marathon runners reveals a ‘hard limit’ on human enduranceAthletes who can run the equivalent of 117 marathons in just months might seem unstoppable. The biggest obstacle, it turns out, is their own bodies. A new study quantifies for the first time an unsurpassable “ceiling” for endurance activities such as long-distance running and biking—and it also finds that pregnancy’s metabolic toll resembles that of an ultramarathon.Ancient molecules reveal surprising details on origins of ‘bizarre’ sloths Email Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwe Sign up for our daily newsletter Get more great content like this delivered right to you! 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